esqueleto-2.5.1: Type-safe EDSL for SQL queries on persistent backends.

Safe Haskell | None
Language | Haskell98

Database.Esqueleto

Contents

- Setup
- Introduction
- Getting started
- `esqueleto`'s Language
  - Joins
- SQL backend
- RDBMS-specific modules
- Helpers
- Re-exports

Description

The `esqueleto` EDSL (embedded domain specific language). This module replaces `Database.Persist`, so instead of importing that module you should just import this one:

    -- For a module using just esqueleto.
    import Database.Esqueleto

If you need to use `persistent`'s default support for queries as well, either import it qualified:

    -- For a module that mostly uses esqueleto.
    import Database.Esqueleto
    import qualified Database.Persist as P

or import `esqueleto` itself qualified:

    -- For a module that uses esqueleto just on some queries.
    import Database.Persist
    import qualified Database.Esqueleto as E

Other than identifier name clashes, `esqueleto` does not conflict with `persistent` in any way.

Synopsis

- class (Functor query, Applicative query, Monad query) => Esqueleto query expr backend | query -> expr backend, expr -> query backend where
- class ToBaseId ent where
  - type BaseEnt ent :: *
- when_ :: expr (Value Bool) -> () -> expr a -> (expr (Value Bool), expr a)
- then_ :: ()
- else_ :: expr a -> expr a
- from :: From query expr backend a => (a -> query b) -> query b
- data Value a = Value a
- unValue :: Value a -> a
- data ValueList a = ValueList a
- data OrderBy
- data DistinctOn
- data LockingKind
  - = ForUpdate
  - | ForShare
  - | LockInShareMode
- class PersistField a => SqlString a
- data InnerJoin a b = a `InnerJoin` b
- data CrossJoin a b = a `CrossJoin` b
- data LeftOuterJoin a b = a `LeftOuterJoin` b
- data RightOuterJoin a b = a `RightOuterJoin` b
- data FullOuterJoin a b = a `FullOuterJoin` b
- data OnClauseWithoutMatchingJoinException = OnClauseWithoutMatchingJoinException String
- data SqlQuery a
- data SqlExpr a
- type SqlEntity ent = (PersistEntity ent, PersistEntityBackend ent ~ SqlBackend)
- select :: (SqlSelect a r, MonadIO m) => SqlQuery a -> SqlReadT m [r]
- selectDistinct :: (SqlSelect a r, MonadIO m) => SqlQuery a -> SqlPersistT m [r]
- selectSource :: (SqlSelect a r, MonadResource m) => SqlQuery a -> Source (SqlPersistT m) r
- selectDistinctSource :: (SqlSelect a r, MonadResource m) => SqlQuery a -> Source (SqlPersistT m) r
- delete :: MonadIO m => SqlQuery () -> SqlWriteT m ()
- deleteCount :: MonadIO m => SqlQuery () -> SqlWriteT m Int64
- update :: (MonadIO m, SqlEntity val) => (SqlExpr (Entity val) -> SqlQuery ()) -> SqlWriteT m ()
- updateCount :: (MonadIO m, SqlEntity val) => (SqlExpr (Entity val) -> SqlQuery ()) -> SqlWriteT m Int64
- insertSelect :: (MonadIO m, PersistEntity a) => SqlQuery (SqlExpr (Insertion a)) -> SqlWriteT m ()
- insertSelectCount :: (MonadIO m, PersistEntity a) => SqlQuery (SqlExpr (Insertion a)) -> SqlWriteT m Int64
- insertSelectDistinct :: (MonadIO m, PersistEntity a) => SqlQuery (SqlExpr (Insertion a)) -> SqlWriteT m ()
- (<#) :: Esqueleto query expr backend => (a -> b) -> expr (Value a) -> expr (Insertion b)
- (<&>) :: Esqueleto query expr backend => expr (Insertion (a -> b)) -> expr (Value a) -> expr (Insertion b)
- valkey :: (Esqueleto query expr backend, ToBackendKey SqlBackend entity, PersistField (Key entity)) => Int64 -> expr (Value (Key entity))
- valJ :: (Esqueleto query expr backend, PersistField (Key entity)) => Value (Key entity) -> expr (Value (Key entity))
- deleteKey :: (PersistStore backend, BaseBackend backend ~ PersistEntityBackend val, MonadIO m, PersistEntity val) => Key val -> ReaderT backend m ()
- module Database.Persist.Sql

# Setup

If you're already using `persistent`, then you're ready to use `esqueleto`, no further setup is needed. If you're just starting a new project and would like to use `esqueleto`, take a look at `persistent`'s book first (http://www.yesodweb.com/book/persistent) to learn how to define your schema.

# Introduction

The main goals of `esqueleto` are to:

- Be easily translatable to SQL. When you take a look at a `esqueleto` query, you should be able to know exactly how the SQL query will end up. (As opposed to being a relational algebra EDSL such as HaskellDB, which is non-trivial to translate into SQL.)
- Support the most widely used SQL features. We'd like you to be able to use `esqueleto` for all of your queries, no exceptions. Send a pull request or open an issue on our project page (https://github.com/prowdsponsor/esqueleto) if there's anything missing that you'd like to see.
- Be as type-safe as possible. We strive to provide as many type checks as possible. If you get bitten by some invalid code that type-checks, please open an issue on our project page so we can take a look.

However, it is not a goal to be able to write portable SQL. We do not try to hide the differences between DBMSs from you, and `esqueleto` code that works for one database may not work on another. This is a compromise we have to make in order to give you as much control over the raw SQL as possible without losing too much convenience. This also means that you may type-check a query that doesn't work on your DBMS.

# Getting started

We like clean, easy-to-read EDSLs. However, in order to achieve this goal we've used a lot of type hackery, leading to some hard-to-read type signatures. On this section, we'll try to build some intuition about the syntax.

For the following examples, we'll use this example schema:

    share [mkPersist sqlSettings, mkMigrate "migrateAll"] [persist|
      Person
        name String
        age Int Maybe
        deriving Eq Show
      BlogPost
        title String
        authorId PersonId
        deriving Eq Show
      Follow
        follower PersonId
        followed PersonId
        deriving Eq Show
    |]

Most of `esqueleto` was created with `SELECT` statements in mind, not only because they're the most common but also because they're the most complex kind of statement. The most simple kind of `SELECT` would be:

    SELECT *
    FROM Person

In `esqueleto`, we may write the same query above as:

    do people <- select $
                 from $ \person -> do
                 return person
       liftIO $ mapM_ (putStrLn . personName . entityVal) people

The expression above has type `SqlPersist m ()`, while `people` has type `[Entity Person]`. The query above will be translated into exactly the same query we wrote manually, but instead of `SELECT *` it will list all entity fields (using `*` is not robust). Note that `esqueleto` knows that we want an `Entity Person` just because of the `personName` that we're printing later.

However, most of the time we need to filter our queries using `WHERE`. For example:

    SELECT *
    FROM Person
    WHERE Person.name = "John"

In `esqueleto`, we may write the same query above as:

    select $
    from $ \p -> do
    where_ (p ^. PersonName ==. val "John")
    return p

Although `esqueleto`'s code is a bit more noisy, it's has almost the same structure (save from the `return`). The `(`^.`)` operator is used to project a field from an entity. The field name is the same one generated by `persistent`'s Template Haskell functions. We use `val` to lift a constant Haskell value into the SQL query.

Another example would be:

    SELECT *
    FROM Person
    WHERE Person.age >= 18

In `esqueleto`, we may write the same query above as:

    select $
    from $ \p -> do
    where_ (p ^. PersonAge >=. just (val 18))
    return p

Since `age` is an optional `Person` field, we use `just` to lift ``val` 18 :: SqlExpr (Value Int)` into `just (`val` 18) :: SqlExpr (Value (Maybe Int))`.

Implicit joins are represented by tuples. For example, to get the list of all blog posts and their authors, we could write:

    SELECT BlogPost.*, Person.*
    FROM BlogPost, Person
    WHERE BlogPost.authorId = Person.id
    ORDER BY BlogPost.title ASC

In `esqueleto`, we may write the same query above as:

    select $
    from $ \(b, p) -> do
    where_ (b ^. BlogPostAuthorId ==. p ^. PersonId)
    orderBy [asc (b ^. BlogPostTitle)]
    return (b, p)

However, you may want your results to include people who don't have any blog posts as well using a `LEFT OUTER JOIN`:

    SELECT Person.*, BlogPost.*
    FROM Person LEFT OUTER JOIN BlogPost
    ON Person.id = BlogPost.authorId
    ORDER BY Person.name ASC, BlogPost.title ASC

In `esqueleto`, we may write the same query above as:

    select $
    from $ \(p `LeftOuterJoin` mb) -> do
    on (just (p ^. PersonId) ==. mb ?. BlogPostAuthorId)
    orderBy [asc (p ^. PersonName), asc (mb ?. BlogPostTitle)]
    return (p, mb)

On a `LEFT OUTER JOIN` the entity on the right hand side may not exist (i.e. there may be a `Person` without any `BlogPost`s), so while `p :: SqlExpr (Entity Person)`, we have `mb :: SqlExpr (Maybe (Entity BlogPost))`. The whole expression above has type `SqlPersist m [(Entity Person, Maybe (Entity BlogPost))]`. Instead of using `(^.)`, we used `(`?.`)` to project a field from a `Maybe (Entity a)`.

We are by no means limited to joins of two tables, nor by joins of different tables. For example, we may want a list of the `Follow` entity:

    SELECT P1.*, Follow.*, P2.*
    FROM Person AS P1
    INNER JOIN Follow ON P1.id = Follow.follower
    INNER JOIN P2 ON P2.id = Follow.followed

In `esqueleto`, we may write the same query above as:

    select $
    from $ \(p1 `InnerJoin` f `InnerJoin` p2) -> do
    on (p2 ^. PersonId ==. f ^. FollowFollowed)
    on (p1 ^. PersonId ==. f ^. FollowFollower)
    return (p1, f, p2)

Note carefully that the order of the ON clauses is reversed! You're required to write your `on`s in reverse order because that helps composability (see the documentation of `on` for more details).

We also currently support `UPDATE` and `DELETE` statements. For example:

    do update $ \p -> do
         set p [ PersonName =. val "João" ]
         where_ (p ^. PersonName ==. val "Joao")
       delete $
         from $ \p -> do
         where_ (p ^. PersonAge <. just (val 14))

The results of queries can also be used for insertions. In `SQL`, we might write the following, inserting a new blog post for every user:

    INSERT INTO BlogPost
    SELECT ('Group Blog Post', id)
    FROM Person

In `esqueleto`, we may write the same query above as:

     insertSelect $ from $ \p->
     return $ BlogPost <# "Group Blog Post" <&> (p ^. PersonId)

Individual insertions can be performed through Persistent's `insert` function, reexported for convenience.

# `esqueleto`'s Language

class (Functor query, Applicative query, Monad query) => Esqueleto query expr backend | query -> expr backend, expr -> query backend where #

Finally tagless representation of `esqueleto`'s EDSL.

Minimal complete definition

fromStart, fromStartMaybe, fromJoin, fromFinish, where_, on, groupBy, orderBy, asc, desc, limit, offset, distinct, distinctOn, don, distinctOnOrderBy, rand, having, locking, sub_select, sub_selectDistinct, (^.), (?.), val, isNothing, just, nothing, joinV, countRows, count, countDistinct, not_, (==.), (>=.), (>.), (<=.), (<.), (!=.), (&&.), (||.), (+.), (-.), (/.), (*.), random_, round_, ceiling_, floor_, sum_, min_, max_, avg_, castNum, castNumM, coalesce, coalesceDefault, lower_, like, ilike, (%), concat_, (++.), castString, subList_select, subList_selectDistinct, valList, justList, in_, notIn, exists, notExists, set, (=.), (+=.), (-=.), (*=.), (/=.), (<#), (<&>), case_, toBaseId

Methods

where_ :: expr (Value Bool) -> query () #

`WHERE` clause: restrict the query's result.

on :: expr (Value Bool) -> query () #

`ON` clause: restrict the a `JOIN`'s result. The `ON` clause will be applied to the last `JOIN` that does not have an `ON` clause yet. If there are no `JOIN`s without `ON` clauses (either because you didn't do any `JOIN`, or because all `JOIN`s already have their own `ON` clauses), a runtime exception `OnClauseWithoutMatchingJoinException` is thrown. `ON` clauses are optional when doing `JOIN`s.

On the simple case of doing just one `JOIN`, for example

    select $
    from $ \(foo `InnerJoin` bar) -> do
      on (foo ^. FooId ==. bar ^. BarFooId)
      ...

there's no ambiguity and the rules above just mean that you're allowed to call `on` only once (as in SQL). If you have many joins, then the `on`s are applied on the reverse order that the `JOIN`s appear. For example:

    select $
    from $ \(foo `InnerJoin` bar `InnerJoin` baz) -> do
      on (baz ^. BazId ==. bar ^. BarBazId)
      on (foo ^. FooId ==. bar ^. BarFooId)
      ...

The order is reversed in order to improve composability. For example, consider `query1` and `query2` below:

    let query1 =
          from $ \(foo `InnerJoin` bar) -> do
            on (foo ^. FooId ==. bar ^. BarFooId)
        query2 =
          from $ \(mbaz `LeftOuterJoin` quux) -> do
            return (mbaz ?. BazName, quux)
        test1 =      (,) <$> query1 <*> query2
        test2 = flip (,) <$> query2 <*> query1

If the order was not reversed, then `test2` would be broken: `query1`'s `on` would refer to `query2`'s `LeftOuterJoin`.

groupBy :: ToSomeValues expr a => a -> query () #

`GROUP BY` clause. You can enclose multiple columns in a tuple.

    select $ from \(foo `InnerJoin` bar) -> do
      on (foo ^. FooBarId ==. bar ^. BarId)
      groupBy (bar ^. BarId, bar ^. BarName)
      return (bar ^. BarId, bar ^. BarName, countRows)

With groupBy you can sort by aggregate functions, like so (we used `let` to restrict the more general `countRows` to `SqlExpr (Value Int)` to avoid ambiguity---the second use of `countRows` has its type restricted by the `:: Int` below):

    r <- select $ from \(foo `InnerJoin` bar) -> do
      on (foo ^. FooBarId ==. bar ^. BarId)
      groupBy $ bar ^. BarName
      let countRows' = countRows
      orderBy [asc countRows']
      return (bar ^. BarName, countRows')
    forM_ r $ \(Value name, Value count) -> do
      print name
      print (count :: Int)

orderBy :: [expr OrderBy] -> query () #

`ORDER BY` clause. See also `asc` and `desc`.

Multiple calls to `orderBy` get concatenated on the final query, including `distinctOnOrderBy`.

asc :: PersistField a => expr (Value a) -> expr OrderBy #

Ascending order of this field or expression.

desc :: PersistField a => expr (Value a) -> expr OrderBy #

Descending order of this field or expression.

limit :: Int64 -> query () #

`LIMIT`. Limit the number of returned rows.

offset :: Int64 -> query () #

`OFFSET`. Usually used with `limit`.

distinct :: query a -> query a #

`DISTINCT`. Change the current `SELECT` into `SELECT DISTINCT`. For example:

    select $ distinct $
      from \foo -> do
      ...

Note that this also has the same effect:

    select $
      from \foo -> do
      distinct (return ())
      ...

Since: 2.2.4

distinctOn :: [expr DistinctOn] -> query a -> query a #

`DISTINCT ON`. Change the current `SELECT` into `SELECT DISTINCT ON (expressions)`. For example:

    select $
      from \foo ->
      distinctOn [don (foo ^. FooName), don (foo ^. FooState)] $ do
      ...

You can also chain different calls to `distinctOn`. The above is equivalent to:

    select $
      from \foo ->
      distinctOn [don (foo ^. FooName)] $
      distinctOn [don (foo ^. FooState)] $ do
      ...

Each call to `distinctOn` adds more expressions. Calls to `distinctOn` override any calls to `distinct`.

Note that PostgreSQL requires the expressions on `DISTINCT ON` to be the first ones to appear on a `ORDER BY`. This is not managed automatically by esqueleto, keeping its spirit of trying to be close to raw SQL.

Supported by PostgreSQL only.

Since: 2.2.4

don :: expr (Value a) -> expr DistinctOn #

Erase an expression's type so that it's suitable to be used by `distinctOn`.

Since: 2.2.4

distinctOnOrderBy :: [expr OrderBy] -> query a -> query a #

A convenience function that calls both `distinctOn` and `orderBy`. In other words,

    distinctOnOrderBy [asc foo, desc bar, desc quux] $ do
      ...

is the same as:

    distinctOn [don foo, don  bar, don  quux] $ do
      orderBy  [asc foo, desc bar, desc quux]
      ...

Since: 2.2.4

rand :: expr OrderBy #

`ORDER BY random()` clause.

Since: 1.3.10

having :: expr (Value Bool) -> query () #

`HAVING`.

Since: 1.2.2

locking :: LockingKind -> query () #

Add a locking clause to the query. Please read `LockingKind` documentation and your RDBMS manual.

If multiple calls to `locking` are made on the same query, the last one is used.

Since: 2.2.7

sub_select :: PersistField a => query (expr (Value a)) -> expr (Value a) #

Execute a subquery `SELECT` in an expression. Returns a simple value so should be used only when the `SELECT` query is guaranteed to return just one row.

sub_selectDistinct :: PersistField a => query (expr (Value a)) -> expr (Value a) #

Deprecated: Since 2.2.4: use `sub_select` and `distinct`.

Same as `sub_select` but using `SELECT DISTINCT`.

(^.) :: (PersistEntity val, PersistField typ) => expr (Entity val) -> EntityField val typ -> expr (Value typ) infixl 9 #

Project a field of an entity.

(?.) :: (PersistEntity val, PersistField typ) => expr (Maybe (Entity val)) -> EntityField val typ -> expr (Value (Maybe typ)) #

Project a field of an entity that may be null.

val :: PersistField typ => typ -> expr (Value typ) #

Lift a constant value from Haskell-land to the query.

isNothing :: PersistField typ => expr (Value (Maybe typ)) -> expr (Value Bool) #

`IS NULL` comparison.

just :: expr (Value typ) -> expr (Value (Maybe typ)) #

Analogous to `Just`, promotes a value of type `typ` into one of type `Maybe typ`. It should hold that ``val` . Just === just . `val``.

nothing :: expr (Value (Maybe typ)) #

`NULL` value.

joinV :: expr (Value (Maybe (Maybe typ))) -> expr (Value (Maybe typ)) #

Join nested `Maybe`s in a `Value` into one. This is useful when calling aggregate functions on nullable fields.

countRows :: Num a => expr (Value a) #

`COUNT(*)` value.

count :: Num a => expr (Value typ) -> expr (Value a) #

`COUNT`.

countDistinct :: Num a => expr (Value typ) -> expr (Value a) #

`COUNT(DISTINCT x)`.

Since: 2.4.1

not_ :: expr (Value Bool) -> expr (Value Bool) #

(==.) :: PersistField typ => expr (Value typ) -> expr (Value typ) -> expr (Value Bool) infix 4 #

(>=.) :: PersistField typ => expr (Value typ) -> expr (Value typ) -> expr (Value Bool) infix 4 #

(>.) :: PersistField typ => expr (Value typ) -> expr (Value typ) -> expr (Value Bool) infix 4 #

(<=.) :: PersistField typ => expr (Value typ) -> expr (Value typ) -> expr (Value Bool) infix 4 #

(<.) :: PersistField typ => expr (Value typ) -> expr (Value typ) -> expr (Value Bool) infix 4 #

(!=.) :: PersistField typ => expr (Value typ) -> expr (Value typ) -> expr (Value Bool) infix 4 #

(&&.) :: expr (Value Bool) -> expr (Value Bool) -> expr (Value Bool) infixr 3 #

(||.) :: expr (Value Bool) -> expr (Value Bool) -> expr (Value Bool) infixr 2 #

(+.) :: PersistField a => expr (Value a) -> expr (Value a) -> expr (Value a) infixl 6 #

(-.) :: PersistField a => expr (Value a) -> expr (Value a) -> expr (Value a) infixl 6 #

(/.) :: PersistField a => expr (Value a) -> expr (Value a) -> expr (Value a) infixl 7 #

(*.) :: PersistField a => expr (Value a) -> expr (Value a) -> expr (Value a) infixl 7 #

random_ :: (PersistField a, Num a) => expr (Value a) #

round_ :: (PersistField a, Num a, PersistField b, Num b) => expr (Value a) -> expr (Value b) #

ceiling_ :: (PersistField a, Num a, PersistField b, Num b) => expr (Value a) -> expr (Value b) #

floor_ :: (PersistField a, Num a, PersistField b, Num b) => expr (Value a) -> expr (Value b) #

sum_ :: (PersistField a, PersistField b) => expr (Value a) -> expr (Value (Maybe b)) #

min_ :: PersistField a => expr (Value a) -> expr (Value (Maybe a)) #

max_ :: PersistField a => expr (Value a) -> expr (Value (Maybe a)) #

avg_ :: (PersistField a, PersistField b) => expr (Value a) -> expr (Value (Maybe b)) #

castNum :: (Num a, Num b) => expr (Value a) -> expr (Value b) #

Allow a number of one type to be used as one of another type via an implicit cast. An explicit cast is not made, this function changes only the types on the Haskell side.

Caveat: Trying to use `castNum` from `Double` to `Int` will not result in an integer, the original fractional number will still be used! Use `round_`, `ceiling_` or `floor_` instead.

Safety: This operation is mostly safe due to the `Num` constraint between the types and the fact that RDBMSs usually allow numbers of different types to be used interchangeably. However, there may still be issues with the query not being accepted by the RDBMS or `persistent` not being able to parse it.

Since: 2.2.9

castNumM :: (Num a, Num b) => expr (Value (Maybe a)) -> expr (Value (Maybe b)) #

Same as `castNum`, but for nullable values.

Since: 2.2.9

coalesce :: PersistField a => [expr (Value (Maybe a))] -> expr (Value (Maybe a)) #

`COALESCE` function. Evaluates the arguments in order and returns the value of the first non-NULL expression, or NULL (Nothing) otherwise. Some RDBMSs (such as SQLite) require at least two arguments; please refer to the appropriate documentation.

Since: 1.4.3

coalesceDefault :: PersistField a => [expr (Value (Maybe a))] -> expr (Value a) -> expr (Value a) #

Like `coalesce`, but takes a non-nullable expression placed at the end of the expression list, which guarantees a non-NULL result.

Since: 1.4.3

lower_ :: SqlString s => expr (Value s) -> expr (Value s) #

`LOWER` function.

like :: SqlString s => expr (Value s) -> expr (Value s) -> expr (Value Bool) infixr 2 #

`LIKE` operator.

ilike :: SqlString s => expr (Value s) -> expr (Value s) -> expr (Value Bool) infixr 2 #

`ILIKE` operator (case-insensitive `LIKE`).

Supported by PostgreSQL only.

Since: 2.2.3

(%) :: SqlString s => expr (Value s) #

The string ``%``. May be useful while using `like` and concatenation (`concat_` or `++.`, depending on your database). Note that you always have to type the parenthesis, for example:

    name `like` (%) ++. val "John" ++. (%)

concat_ :: SqlString s => [expr (Value s)] -> expr (Value s) #

The `CONCAT` function with a variable number of parameters. Supported by MySQL and PostgreSQL.

(++.) :: SqlString s => expr (Value s) -> expr (Value s) -> expr (Value s) infixr 5 #

The `||` string concatenation operator (named after Haskell's `++` in order to avoid naming clash with `||.`). Supported by SQLite and PostgreSQL.

castString :: (SqlString s, SqlString r) => expr (Value s) -> expr (Value r) #

Cast a string type into `Text`. This function is very useful if you want to use `newtype`s, or if you want to apply functions such as `like` to strings of different types.

Safety: This is a slightly unsafe function, especially if you have defined your own instances of `SqlString`. Also, since `Maybe` is an instance of `SqlString`, it's possible to turn a nullable value into a non-nullable one. Avoid using this function if possible.

subList_select :: PersistField a => query (expr (Value a)) -> expr (ValueList a) #

Execute a subquery `SELECT` in an expression. Returns a list of values.

subList_selectDistinct :: PersistField a => query (expr (Value a)) -> expr (ValueList a) #

Deprecated: Since 2.2.4: use `subList_select` and `distinct`.

Same as `sublist_select` but using `SELECT DISTINCT`.

valList :: PersistField typ => [typ] -> expr (ValueList typ) #

Lift a list of constant value from Haskell-land to the query.

justList :: expr (ValueList typ) -> expr (ValueList (Maybe typ)) #

Same as `just` but for `ValueList`. Most of the time you won't need it, though, because you can use `just` from inside `subList_select` or `Just` from inside `valList`.

Since: 2.2.12

in_ :: PersistField typ => expr (Value typ) -> expr (ValueList typ) -> expr (Value Bool) #

`IN` operator. For example if you want to select all `Person`s by a list of IDs:

    SELECT *
    FROM Person
    WHERE Person.id IN (?)

In `esqueleto`, we may write the same query above as:

    select $
    from $ \person -> do
    where_ $ person ^. PersonId `in_` valList personIds
    return person

Where `personIds` is of type `[Key Person]`.

notIn :: PersistField typ => expr (Value typ) -> expr (ValueList typ) -> expr (Value Bool) #

`NOT IN` operator.

exists :: query () -> expr (Value Bool) #

`EXISTS` operator. For example:

    select $
    from $ \person -> do
    where_ $ exists $
             from $ \post -> do
             where_ (post ^. BlogPostAuthorId ==. person ^. PersonId)
    return person

notExists :: query () -> expr (Value Bool) #

`NOT EXISTS` operator.

set :: PersistEntity val => expr (Entity val) -> [expr (Update val)] -> query () #

`SET` clause used on `UPDATE`s. Note that while it's not a type error to use this function on a `SELECT`, it will most certainly result in a runtime error.

(=.) :: (PersistEntity val, PersistField typ) => EntityField val typ -> expr (Value typ) -> expr (Update val) infixr 3 #

(+=.) :: (PersistEntity val, PersistField a) => EntityField val a -> expr (Value a) -> expr (Update val) infixr 3 #

(-=.) :: (PersistEntity val, PersistField a) => EntityField val a -> expr (Value a) -> expr (Update val) infixr 3 #

(*=.) :: (PersistEntity val, PersistField a) => EntityField val a -> expr (Value a) -> expr (Update val) infixr 3 #

(/=.) :: (PersistEntity val, PersistField a) => EntityField val a -> expr (Value a) -> expr (Update val) infixr 3 #

(<#) :: (a -> b) -> expr (Value a) -> expr (Insertion b) #

Apply a `PersistField` constructor to `expr Value` arguments.

(<&>) :: expr (Insertion (a -> b)) -> expr (Value a) -> expr (Insertion b) #

Apply extra `expr Value` arguments to a `PersistField` constructor

case_ :: PersistField a => [(expr (Value Bool), expr (Value a))] -> expr (Value a) -> expr (Value a) #

`CASE` statement. For example:

    select $
    return $
    case_
       [ when_
           (exists $
           from $ \p -> do
           where_ (p ^. PersonName ==. val "Mike"))
         then_
           (sub_select $
           from $ \v -> do
           let sub =
                   from $ \c -> do
                   where_ (c ^. PersonName ==. val "Mike")
                   return (c ^. PersonFavNum)
           where_ (v ^. PersonFavNum >. sub_select sub)
           return $ count (v ^. PersonName) +. val (1 :: Int)) ]
       (else_ $ val (-1))

This query is a bit complicated, but basically it checks if a person named `"Mike"` exists, and if that person does, run the subquery to find out how many people have a ranking (by Fav Num) higher than `"Mike"`.

NOTE: There are a few things to be aware about this statement.

- This only implements the full CASE statement, it does not implement the "simple" CASE statement.
- At least one `when_` and `then_` is mandatory otherwise it will emit an error.
- The `else_` is also mandatory, unlike the SQL statement in which if the `ELSE` is omitted it will return a `NULL`. You can reproduce this via `nothing`.

Since: 2.1.2

toBaseId :: ToBaseId ent => expr (Value (Key ent)) -> expr (Value (Key (BaseEnt ent))) #

Convert an entity's key into another entity's.

This function is to be used when you change an entity's `Id` to be that of another entity. For example:

    Bar
      barNum Int
    Foo
      Id BarId
      fooNum Int

For this example, declare:

    instance ToBaseId Foo where
      type BaseEnt Foo = Bar
      toBaseIdWitness = FooKey

Now you're able to write queries such as:

    select $
    from $ (bar `InnerJoin` foo) -> do
    on (toBaseId (foo ^. FooId) ==. bar ^. BarId)
    return (bar, foo)

Note: this function may be unsafe to use in conditions not like the one of the example above.

Since: 2.4.3

Instances

Esqueleto SqlQuery SqlExpr SqlBackend # |
Methods fromStart :: (PersistEntity a, (* ~ PersistEntityBackend a) SqlBackend) => SqlQuery (SqlExpr (PreprocessedFrom (SqlExpr (Entity a)))) # fromStartMaybe :: (PersistEntity a, (* ~ PersistEntityBackend a) SqlBackend) => SqlQuery (SqlExpr (PreprocessedFrom (SqlExpr (Maybe (Entity a))))) # fromJoin :: IsJoinKind join => SqlExpr (PreprocessedFrom a) -> SqlExpr (PreprocessedFrom b) -> SqlQuery (SqlExpr (PreprocessedFrom (join a b))) # fromFinish :: SqlExpr (PreprocessedFrom a) -> SqlQuery a # where_ :: SqlExpr (Value Bool) -> SqlQuery () # on :: SqlExpr (Value Bool) -> SqlQuery () # groupBy :: ToSomeValues SqlExpr a => a -> SqlQuery () # orderBy :: [SqlExpr OrderBy] -> SqlQuery () # asc :: PersistField a => SqlExpr (Value a) -> SqlExpr OrderBy # desc :: PersistField a => SqlExpr (Value a) -> SqlExpr OrderBy # limit :: Int64 -> SqlQuery () # offset :: Int64 -> SqlQuery () # distinct :: SqlQuery a -> SqlQuery a # distinctOn :: [SqlExpr DistinctOn] -> SqlQuery a -> SqlQuery a # don :: SqlExpr (Value a) -> SqlExpr DistinctOn # distinctOnOrderBy :: [SqlExpr OrderBy] -> SqlQuery a -> SqlQuery a # rand :: SqlExpr OrderBy # having :: SqlExpr (Value Bool) -> SqlQuery () # locking :: LockingKind -> SqlQuery () # sub_select :: PersistField a => SqlQuery (SqlExpr (Value a)) -> SqlExpr (Value a) # sub_selectDistinct :: PersistField a => SqlQuery (SqlExpr (Value a)) -> SqlExpr (Value a) # (^.) :: (PersistEntity val, PersistField typ) => SqlExpr (Entity val) -> EntityField val typ -> SqlExpr (Value typ) # (?.) :: (PersistEntity val, PersistField typ) => SqlExpr (Maybe (Entity val)) -> EntityField val typ -> SqlExpr (Value (Maybe typ)) # val :: PersistField typ => typ -> SqlExpr (Value typ) # isNothing :: PersistField typ => SqlExpr (Value (Maybe typ)) -> SqlExpr (Value Bool) # just :: SqlExpr (Value typ) -> SqlExpr (Value (Maybe typ)) # nothing :: SqlExpr (Value (Maybe typ)) # joinV :: SqlExpr (Value (Maybe (Maybe typ))) -> SqlExpr (Value (Maybe typ)) # countRows :: Num a => SqlExpr (Value a) # count :: Num a => SqlExpr (Value typ) -> SqlExpr (Value a) # countDistinct :: Num a => SqlExpr (Value typ) -> SqlExpr (Value a) # not_ :: SqlExpr (Value Bool) -> SqlExpr (Value Bool) # (==.) :: PersistField typ => SqlExpr (Value typ) -> SqlExpr (Value typ) -> SqlExpr (Value Bool) # (>=.) :: PersistField typ => SqlExpr (Value typ) -> SqlExpr (Value typ) -> SqlExpr (Value Bool) # (>.) :: PersistField typ => SqlExpr (Value typ) -> SqlExpr (Value typ) -> SqlExpr (Value Bool) # (<=.) :: PersistField typ => SqlExpr (Value typ) -> SqlExpr (Value typ) -> SqlExpr (Value Bool) # (<.) :: PersistField typ => SqlExpr (Value typ) -> SqlExpr (Value typ) -> SqlExpr (Value Bool) # (!=.) :: PersistField typ => SqlExpr (Value typ) -> SqlExpr (Value typ) -> SqlExpr (Value Bool) # (&&.) :: SqlExpr (Value Bool) -> SqlExpr (Value Bool) -> SqlExpr (Value Bool) # (||.) :: SqlExpr (Value Bool) -> SqlExpr (Value Bool) -> SqlExpr (Value Bool) # (+.) :: PersistField a => SqlExpr (Value a) -> SqlExpr (Value a) -> SqlExpr (Value a) # (-.) :: PersistField a => SqlExpr (Value a) -> SqlExpr (Value a) -> SqlExpr (Value a) # (/.) :: PersistField a => SqlExpr (Value a) -> SqlExpr (Value a) -> SqlExpr (Value a) # (*.) :: PersistField a => SqlExpr (Value a) -> SqlExpr (Value a) -> SqlExpr (Value a) # random_ :: (PersistField a, Num a) => SqlExpr (Value a) # round_ :: (PersistField a, Num a, PersistField b, Num b) => SqlExpr (Value a) -> SqlExpr (Value b) # ceiling_ :: (PersistField a, Num a, PersistField b, Num b) => SqlExpr (Value a) -> SqlExpr (Value b) # floor_ :: (PersistField a, Num a, PersistField b, Num b) => SqlExpr (Value a) -> SqlExpr (Value b) # sum_ :: (PersistField a, PersistField b) => SqlExpr (Value a) -> SqlExpr (Value (Maybe b)) # min_ :: PersistField a => SqlExpr (Value a) -> SqlExpr (Value (Maybe a)) # max_ :: PersistField a => SqlExpr (Value a) -> SqlExpr (Value (Maybe a)) # avg_ :: (PersistField a, PersistField b) => SqlExpr (Value a) -> SqlExpr (Value (Maybe b)) # castNum :: (Num a, Num b) => SqlExpr (Value a) -> SqlExpr (Value b) # castNumM :: (Num a, Num b) => SqlExpr (Value (Maybe a)) -> SqlExpr (Value (Maybe b)) # coalesce :: PersistField a => [SqlExpr (Value (Maybe a))] -> SqlExpr (Value (Maybe a)) # coalesceDefault :: PersistField a => [SqlExpr (Value (Maybe a))] -> SqlExpr (Value a) -> SqlExpr (Value a) # lower_ :: SqlString s => SqlExpr (Value s) -> SqlExpr (Value s) # like :: SqlString s => SqlExpr (Value s) -> SqlExpr (Value s) -> SqlExpr (Value Bool) # ilike :: SqlString s => SqlExpr (Value s) -> SqlExpr (Value s) -> SqlExpr (Value Bool) # (%) :: SqlString s => SqlExpr (Value s) # concat_ :: SqlString s => [SqlExpr (Value s)] -> SqlExpr (Value s) # (++.) :: SqlString s => SqlExpr (Value s) -> SqlExpr (Value s) -> SqlExpr (Value s) # castString :: (SqlString s, SqlString r) => SqlExpr (Value s) -> SqlExpr (Value r) # subList_select :: PersistField a => SqlQuery (SqlExpr (Value a)) -> SqlExpr (ValueList a) # subList_selectDistinct :: PersistField a => SqlQuery (SqlExpr (Value a)) -> SqlExpr (ValueList a) # valList :: PersistField typ => [typ] -> SqlExpr (ValueList typ) # justList :: SqlExpr (ValueList typ) -> SqlExpr (ValueList (Maybe typ)) # in_ :: PersistField typ => SqlExpr (Value typ) -> SqlExpr (ValueList typ) -> SqlExpr (Value Bool) # notIn :: PersistField typ => SqlExpr (Value typ) -> SqlExpr (ValueList typ) -> SqlExpr (Value Bool) # exists :: SqlQuery () -> SqlExpr (Value Bool) # notExists :: SqlQuery () -> SqlExpr (Value Bool) # set :: PersistEntity val => SqlExpr (Entity val) -> [SqlExpr (Update val)] -> SqlQuery () # (=.) :: (PersistEntity val, PersistField typ) => EntityField val typ -> SqlExpr (Value typ) -> SqlExpr (Update val) # (+=.) :: (PersistEntity val, PersistField a) => EntityField val a -> SqlExpr (Value a) -> SqlExpr (Update val) # (-=.) :: (PersistEntity val, PersistField a) => EntityField val a -> SqlExpr (Value a) -> SqlExpr (Update val) # (*=.) :: (PersistEntity val, PersistField a) => EntityField val a -> SqlExpr (Value a) -> SqlExpr (Update val) # (/=.) :: (PersistEntity val, PersistField a) => EntityField val a -> SqlExpr (Value a) -> SqlExpr (Update val) # (<#) :: (a -> b) -> SqlExpr (Value a) -> SqlExpr (Insertion b) # (<&>) :: SqlExpr (Insertion (a -> b)) -> SqlExpr (Value a) -> SqlExpr (Insertion b) # case_ :: PersistField a => [(SqlExpr (Value Bool), SqlExpr (Value a))] -> SqlExpr (Value a) -> SqlExpr (Value a) # toBaseId :: ToBaseId ent => SqlExpr (Value (Key ent)) -> SqlExpr (Value (Key (BaseEnt ent))) #

class ToBaseId ent where #

Class that enables one to use `toBaseId` to convert an entity's key on a query into another (cf. `toBaseId`).

Minimal complete definition

toBaseIdWitness

Associated Types

type BaseEnt ent :: * #

Methods

toBaseIdWitness :: Key (BaseEnt ent) -> Key ent #

when_ :: expr (Value Bool) -> () -> expr a -> (expr (Value Bool), expr a) #

Syntax sugar for `case_`.

Since: 2.1.2

then_ :: () #

Syntax sugar for `case_`.

Since: 2.1.2

else_ :: expr a -> expr a #

Syntax sugar for `case_`.

Since: 2.1.2

from :: From query expr backend a => (a -> query b) -> query b #

`FROM` clause: bring entities into scope.

This function internally uses two type classes in order to provide some flexibility of how you may call it. Internally we refer to these type classes as the two different magics.

The innermost magic allows you to use `from` with the following types:

- `expr (Entity val)`, which brings a single entity into scope.
- `expr (Maybe (Entity val))`, which brings a single entity that may be `NULL` into scope. Used for `OUTER JOIN`s.
- A `JOIN` of any other two types allowed by the innermost magic, where a `JOIN` may be an `InnerJoin`, a `CrossJoin`, a `LeftOuterJoin`, a `RightOuterJoin`, or a `FullOuterJoin`. The `JOINs` have left fixity.

The outermost magic allows you to use `from` on any tuples of types supported by innermost magic (and also tuples of tuples, and so on), up to 8-tuples.

Note that using `from` for the same entity twice does work and corresponds to a self-join. You don't even need to use two different calls to `from`, you may use a `JOIN` or a tuple.

The following are valid examples of uses of `from` (the types of the arguments of the lambda are inside square brackets):

    from $ \person -> ...
    from $ \(person, blogPost) -> ...
    from $ \(p `LeftOuterJoin` mb) -> ...
    from $ \(p1 `InnerJoin` f `InnerJoin` p2) -> ...
    from $ \((p1 `InnerJoin` f) `InnerJoin` p2) -> ...

The types of the arguments to the lambdas above are, respectively:

    person
      :: ( Esqueleto query expr backend
         , PersistEntity Person
         , PersistEntityBackend Person ~ backend
         ) => expr (Entity Person)
    (person, blogPost)
      :: (...) => (expr (Entity Person), expr (Entity BlogPost))
    (p `LeftOuterJoin` mb)
      :: (...) => InnerJoin (expr (Entity Person)) (expr (Maybe (Entity BlogPost)))
    (p1 `InnerJoin` f `InnerJoin` p2)
      :: (...) => InnerJoin
                    (InnerJoin (expr (Entity Person))
                               (expr (Entity Follow)))
                    (expr (Entity Person))
    (p1 `InnerJoin` (f `InnerJoin` p2)) ::
      :: (...) => InnerJoin
                    (expr (Entity Person))
                    (InnerJoin (expr (Entity Follow))
                               (expr (Entity Person)))

Note that some backends may not support all kinds of `JOIN`s.

data Value a #

A single value (as opposed to a whole entity). You may use `(`^.`)` or `(`?.`)` to get a `Value` from an `Entity`.

Constructors

Value a |

Instances

Functor Value # | Since: 1.4.4
Methods fmap :: (a -> b) -> Value a -> Value b # (<$) :: a -> Value b -> Value a #
ToSomeValues SqlExpr (SqlExpr (Value a)) # |
Methods toSomeValues :: SqlExpr (Value a) -> [SomeValue SqlExpr] #
Eq a => Eq (Value a) # |
Methods (==) :: Value a -> Value a -> Bool # (/=) :: Value a -> Value a -> Bool #
Ord a => Ord (Value a) # |
Methods compare :: Value a -> Value a -> Ordering # (<) :: Value a -> Value a -> Bool # (<=) :: Value a -> Value a -> Bool # (>) :: Value a -> Value a -> Bool # (>=) :: Value a -> Value a -> Bool # max :: Value a -> Value a -> Value a # min :: Value a -> Value a -> Value a #
Show a => Show (Value a) # |
Methods showsPrec :: Int -> Value a -> ShowS # show :: Value a -> String # showList :: [Value a] -> ShowS #
PersistField a => SqlSelect (SqlExpr (Value a)) (Value a) # | You may return any single value (i.e. a single column) from a `select` query.
Methods sqlSelectCols :: IdentInfo -> SqlExpr (Value a) -> (Builder, [PersistValue]) # sqlSelectColCount :: Proxy * (SqlExpr (Value a)) -> Int # sqlSelectProcessRow :: [PersistValue] -> Either Text (Value a) # sqlInsertInto :: IdentInfo -> SqlExpr (Value a) -> (Builder, [PersistValue]) #

unValue :: Value a -> a #

Unwrap a `Value`.

Since: 1.4.1

data ValueList a #

A list of single values. There's a limited set of functions able to work with this data type (such as `subList_select`, `valList`, `in_` and `exists`).

Constructors

ValueList a |

Instances

Eq a => Eq (ValueList a) # |
Methods (==) :: ValueList a -> ValueList a -> Bool # (/=) :: ValueList a -> ValueList a -> Bool #
Ord a => Ord (ValueList a) # |
Methods compare :: ValueList a -> ValueList a -> Ordering # (<) :: ValueList a -> ValueList a -> Bool # (<=) :: ValueList a -> ValueList a -> Bool # (>) :: ValueList a -> ValueList a -> Bool # (>=) :: ValueList a -> ValueList a -> Bool # max :: ValueList a -> ValueList a -> ValueList a # min :: ValueList a -> ValueList a -> ValueList a #
Show a => Show (ValueList a) # |
Methods showsPrec :: Int -> ValueList a -> ShowS # show :: ValueList a -> String # showList :: [ValueList a] -> ShowS #

data OrderBy #

Phantom type used by `orderBy`, `asc` and `desc`.

data DistinctOn #

Phantom type used by `distinctOn` and `don`.

data LockingKind #

Different kinds of locking clauses supported by `locking`.

Note that each RDBMS has different locking support. The constructors of this datatype specify only the syntax of the locking mechanism, not its semantics. For example, even though both MySQL and PostgreSQL support `ForUpdate`, there are no guarantees that they will behave the same.

Since: 2.2.7

Constructors

ForUpdate | `FOR UPDATE` syntax. Supported by MySQL, Oracle and PostgreSQL. Since: 2.2.7
ForShare | `FOR SHARE` syntax. Supported by PostgreSQL. Since: 2.2.7
LockInShareMode | `LOCK IN SHARE MODE` syntax. Supported by MySQL. Since: 2.2.7

class PersistField a => SqlString a #

Phantom class of data types that are treated as strings by the RDBMS. It has no methods because it's only used to avoid type errors such as trying to concatenate integers.

If you have a custom data type or `newtype`, feel free to make it an instance of this class.

Since: 2.4.0

Instances

SqlString ByteString # | Since: 2.3.0
SqlString Text # | Since: 2.3.0
SqlString Text # | Since: 2.3.0
SqlString Html # | Since: 2.3.0
(~) * a Char => SqlString [a] # | Since: 2.3.0
SqlString a => SqlString (Maybe a) # | Since: 2.4.0

## Joins

data InnerJoin a b infixl 2 #

Data type that represents an `INNER JOIN` (see `LeftOuterJoin` for an example).

Constructors

a `InnerJoin` b infixl 2 |

Instances

IsJoinKind InnerJoin # |
Methods smartJoin :: a -> b -> InnerJoin a b # reifyJoinKind :: InnerJoin a b -> JoinKind #
(Esqueleto query expr backend, FromPreprocess query expr backend (InnerJoin a b)) => From query expr backend (InnerJoin a b) # |
Methods from_ :: query (InnerJoin a b)

data CrossJoin a b infixl 2 #

Data type that represents a `CROSS JOIN` (see `LeftOuterJoin` for an example).

Constructors

a `CrossJoin` b infixl 2 |

Instances

IsJoinKind CrossJoin # |
Methods smartJoin :: a -> b -> CrossJoin a b # reifyJoinKind :: CrossJoin a b -> JoinKind #
(Esqueleto query expr backend, FromPreprocess query expr backend (CrossJoin a b)) => From query expr backend (CrossJoin a b) # |
Methods from_ :: query (CrossJoin a b)

data LeftOuterJoin a b infixl 2 #

Data type that represents a `LEFT OUTER JOIN`. For example,

    select $
    from $ \(person `LeftOuterJoin` pet) ->
      ...

is translated into

    SELECT ...
    FROM Person LEFT OUTER JOIN Pet
    ...

See also: `from`.

Constructors

a `LeftOuterJoin` b infixl 2 |

Instances

IsJoinKind LeftOuterJoin # |
Methods smartJoin :: a -> b -> LeftOuterJoin a b # reifyJoinKind :: LeftOuterJoin a b -> JoinKind #
(Esqueleto query expr backend, FromPreprocess query expr backend (LeftOuterJoin a b)) => From query expr backend (LeftOuterJoin a b) # |
Methods from_ :: query (LeftOuterJoin a b)

data RightOuterJoin a b infixl 2 #

Data type that represents a `RIGHT OUTER JOIN` (see `LeftOuterJoin` for an example).

Constructors

a `RightOuterJoin` b infixl 2 |

Instances

IsJoinKind RightOuterJoin # |
Methods smartJoin :: a -> b -> RightOuterJoin a b # reifyJoinKind :: RightOuterJoin a b -> JoinKind #
(Esqueleto query expr backend, FromPreprocess query expr backend (RightOuterJoin a b)) => From query expr backend (RightOuterJoin a b) # |
Methods from_ :: query (RightOuterJoin a b)

data FullOuterJoin a b infixl 2 #

Data type that represents a `FULL OUTER JOIN` (see `LeftOuterJoin` for an example).

Constructors

a `FullOuterJoin` b infixl 2 |

Instances

IsJoinKind FullOuterJoin # |
Methods smartJoin :: a -> b -> FullOuterJoin a b # reifyJoinKind :: FullOuterJoin a b -> JoinKind #
(Esqueleto query expr backend, FromPreprocess query expr backend (FullOuterJoin a b)) => From query expr backend (FullOuterJoin a b) # |
Methods from_ :: query (FullOuterJoin a b)

data OnClauseWithoutMatchingJoinException #

Exception thrown whenever `on` is used to create an `ON` clause but no matching `JOIN` is found.

Constructors

OnClauseWithoutMatchingJoinException String |

Instances

Eq OnClauseWithoutMatchingJoinException # |
Methods (==) :: OnClauseWithoutMatchingJoinException -> OnClauseWithoutMatchingJoinException -> Bool # (/=) :: OnClauseWithoutMatchingJoinException -> OnClauseWithoutMatchingJoinException -> Bool #
Ord OnClauseWithoutMatchingJoinException # |
Methods compare :: OnClauseWithoutMatchingJoinException -> OnClauseWithoutMatchingJoinException -> Ordering # (<) :: OnClauseWithoutMatchingJoinException -> OnClauseWithoutMatchingJoinException -> Bool # (<=) :: OnClauseWithoutMatchingJoinException -> OnClauseWithoutMatchingJoinException -> Bool # (>) :: OnClauseWithoutMatchingJoinException -> OnClauseWithoutMatchingJoinException -> Bool # (>=) :: OnClauseWithoutMatchingJoinException -> OnClauseWithoutMatchingJoinException -> Bool # max :: OnClauseWithoutMatchingJoinException -> OnClauseWithoutMatchingJoinException -> OnClauseWithoutMatchingJoinException # min :: OnClauseWithoutMatchingJoinException -> OnClauseWithoutMatchingJoinException -> OnClauseWithoutMatchingJoinException #
Show OnClauseWithoutMatchingJoinException # |
Methods showsPrec :: Int -> OnClauseWithoutMatchingJoinException -> ShowS # show :: OnClauseWithoutMatchingJoinException -> String # showList :: [OnClauseWithoutMatchingJoinException] -> ShowS #
Exception OnClauseWithoutMatchingJoinException # |
Methods toException :: OnClauseWithoutMatchingJoinException -> SomeException # fromException :: SomeException -> Maybe OnClauseWithoutMatchingJoinException # displayException :: OnClauseWithoutMatchingJoinException -> String #

# SQL backend

data SqlQuery a #

SQL backend for `esqueleto` using `SqlPersistT`.

Instances

Monad SqlQuery # |
Methods (>>=) :: SqlQuery a -> (a -> SqlQuery b) -> SqlQuery b # (>>) :: SqlQuery a -> SqlQuery b -> SqlQuery b # return :: a -> SqlQuery a # fail :: String -> SqlQuery a #
Functor SqlQuery # |
Methods fmap :: (a -> b) -> SqlQuery a -> SqlQuery b # (<$) :: a -> SqlQuery b -> SqlQuery a #
Applicative SqlQuery # |
Methods pure :: a -> SqlQuery a # (<*>) :: SqlQuery (a -> b) -> SqlQuery a -> SqlQuery b # (*>) :: SqlQuery a -> SqlQuery b -> SqlQuery b # (<*) :: SqlQuery a -> SqlQuery b -> SqlQuery a #
Esqueleto SqlQuery SqlExpr SqlBackend # |
Methods fromStart :: (PersistEntity a, (* ~ PersistEntityBackend a) SqlBackend) => SqlQuery (SqlExpr (PreprocessedFrom (SqlExpr (Entity a)))) # fromStartMaybe :: (PersistEntity a, (* ~ PersistEntityBackend a) SqlBackend) => SqlQuery (SqlExpr (PreprocessedFrom (SqlExpr (Maybe (Entity a))))) # fromJoin :: IsJoinKind join => SqlExpr (PreprocessedFrom a) -> SqlExpr (PreprocessedFrom b) -> SqlQuery (SqlExpr (PreprocessedFrom (join a b))) # fromFinish :: SqlExpr (PreprocessedFrom a) -> SqlQuery a # where_ :: SqlExpr (Value Bool) -> SqlQuery () # on :: SqlExpr (Value Bool) -> SqlQuery () # groupBy :: ToSomeValues SqlExpr a => a -> SqlQuery () # orderBy :: [SqlExpr OrderBy] -> SqlQuery () # asc :: PersistField a => SqlExpr (Value a) -> SqlExpr OrderBy # desc :: PersistField a => SqlExpr (Value a) -> SqlExpr OrderBy # limit :: Int64 -> SqlQuery () # offset :: Int64 -> SqlQuery () # distinct :: SqlQuery a -> SqlQuery a # distinctOn :: [SqlExpr DistinctOn] -> SqlQuery a -> SqlQuery a # don :: SqlExpr (Value a) -> SqlExpr DistinctOn # distinctOnOrderBy :: [SqlExpr OrderBy] -> SqlQuery a -> SqlQuery a # rand :: SqlExpr OrderBy # having :: SqlExpr (Value Bool) -> SqlQuery () # locking :: LockingKind -> SqlQuery () # sub_select :: PersistField a => SqlQuery (SqlExpr (Value a)) -> SqlExpr (Value a) # sub_selectDistinct :: PersistField a => SqlQuery (SqlExpr (Value a)) -> SqlExpr (Value a) # (^.) :: (PersistEntity val, PersistField typ) => SqlExpr (Entity val) -> EntityField val typ -> SqlExpr (Value typ) # (?.) :: (PersistEntity val, PersistField typ) => SqlExpr (Maybe (Entity val)) -> EntityField val typ -> SqlExpr (Value (Maybe typ)) # val :: PersistField typ => typ -> SqlExpr (Value typ) # isNothing :: PersistField typ => SqlExpr (Value (Maybe typ)) -> SqlExpr (Value Bool) # just :: SqlExpr (Value typ) -> SqlExpr (Value (Maybe typ)) # nothing :: SqlExpr (Value (Maybe typ)) # joinV :: SqlExpr (Value (Maybe (Maybe typ))) -> SqlExpr (Value (Maybe typ)) # countRows :: Num a => SqlExpr (Value a) # count :: Num a => SqlExpr (Value typ) -> SqlExpr (Value a) # countDistinct :: Num a => SqlExpr (Value typ) -> SqlExpr (Value a) # not_ :: SqlExpr (Value Bool) -> SqlExpr (Value Bool) # (==.) :: PersistField typ => SqlExpr (Value typ) -> SqlExpr (Value typ) -> SqlExpr (Value Bool) # (>=.) :: PersistField typ => SqlExpr (Value typ) -> SqlExpr (Value typ) -> SqlExpr (Value Bool) # (>.) :: PersistField typ => SqlExpr (Value typ) -> SqlExpr (Value typ) -> SqlExpr (Value Bool) # (<=.) :: PersistField typ => SqlExpr (Value typ) -> SqlExpr (Value typ) -> SqlExpr (Value Bool) # (<.) :: PersistField typ => SqlExpr (Value typ) -> SqlExpr (Value typ) -> SqlExpr (Value Bool) # (!=.) :: PersistField typ => SqlExpr (Value typ) -> SqlExpr (Value typ) -> SqlExpr (Value Bool) # (&&.) :: SqlExpr (Value Bool) -> SqlExpr (Value Bool) -> SqlExpr (Value Bool) # (||.) :: SqlExpr (Value Bool) -> SqlExpr (Value Bool) -> SqlExpr (Value Bool) # (+.) :: PersistField a => SqlExpr (Value a) -> SqlExpr (Value a) -> SqlExpr (Value a) # (-.) :: PersistField a => SqlExpr (Value a) -> SqlExpr (Value a) -> SqlExpr (Value a) # (/.) :: PersistField a => SqlExpr (Value a) -> SqlExpr (Value a) -> SqlExpr (Value a) # (*.) :: PersistField a => SqlExpr (Value a) -> SqlExpr (Value a) -> SqlExpr (Value a) # random_ :: (PersistField a, Num a) => SqlExpr (Value a) # round_ :: (PersistField a, Num a, PersistField b, Num b) => SqlExpr (Value a) -> SqlExpr (Value b) # ceiling_ :: (PersistField a, Num a, PersistField b, Num b) => SqlExpr (Value a) -> SqlExpr (Value b) # floor_ :: (PersistField a, Num a, PersistField b, Num b) => SqlExpr (Value a) -> SqlExpr (Value b) # sum_ :: (PersistField a, PersistField b) => SqlExpr (Value a) -> SqlExpr (Value (Maybe b)) # min_ :: PersistField a => SqlExpr (Value a) -> SqlExpr (Value (Maybe a)) # max_ :: PersistField a => SqlExpr (Value a) -> SqlExpr (Value (Maybe a)) # avg_ :: (PersistField a, PersistField b) => SqlExpr (Value a) -> SqlExpr (Value (Maybe b)) # castNum :: (Num a, Num b) => SqlExpr (Value a) -> SqlExpr (Value b) # castNumM :: (Num a, Num b) => SqlExpr (Value (Maybe a)) -> SqlExpr (Value (Maybe b)) # coalesce :: PersistField a => [SqlExpr (Value (Maybe a))] -> SqlExpr (Value (Maybe a)) # coalesceDefault :: PersistField a => [SqlExpr (Value (Maybe a))] -> SqlExpr (Value a) -> SqlExpr (Value a) # lower_ :: SqlString s => SqlExpr (Value s) -> SqlExpr (Value s) # like :: SqlString s => SqlExpr (Value s) -> SqlExpr (Value s) -> SqlExpr (Value Bool) # ilike :: SqlString s => SqlExpr (Value s) -> SqlExpr (Value s) -> SqlExpr (Value Bool) # (%) :: SqlString s => SqlExpr (Value s) # concat_ :: SqlString s => [SqlExpr (Value s)] -> SqlExpr (Value s) # (++.) :: SqlString s => SqlExpr (Value s) -> SqlExpr (Value s) -> SqlExpr (Value s) # castString :: (SqlString s, SqlString r) => SqlExpr (Value s) -> SqlExpr (Value r) # subList_select :: PersistField a => SqlQuery (SqlExpr (Value a)) -> SqlExpr (ValueList a) # subList_selectDistinct :: PersistField a => SqlQuery (SqlExpr (Value a)) -> SqlExpr (ValueList a) # valList :: PersistField typ => [typ] -> SqlExpr (ValueList typ) # justList :: SqlExpr (ValueList typ) -> SqlExpr (ValueList (Maybe typ)) # in_ :: PersistField typ => SqlExpr (Value typ) -> SqlExpr (ValueList typ) -> SqlExpr (Value Bool) # notIn :: PersistField typ => SqlExpr (Value typ) -> SqlExpr (ValueList typ) -> SqlExpr (Value Bool) # exists :: SqlQuery () -> SqlExpr (Value Bool) # notExists :: SqlQuery () -> SqlExpr (Value Bool) # set :: PersistEntity val => SqlExpr (Entity val) -> [SqlExpr (Update val)] -> SqlQuery () # (=.) :: (PersistEntity val, PersistField typ) => EntityField val typ -> SqlExpr (Value typ) -> SqlExpr (Update val) # (+=.) :: (PersistEntity val, PersistField a) => EntityField val a -> SqlExpr (Value a) -> SqlExpr (Update val) # (-=.) :: (PersistEntity val, PersistField a) => EntityField val a -> SqlExpr (Value a) -> SqlExpr (Update val) # (*=.) :: (PersistEntity val, PersistField a) => EntityField val a -> SqlExpr (Value a) -> SqlExpr (Update val) # (/=.) :: (PersistEntity val, PersistField a) => EntityField val a -> SqlExpr (Value a) -> SqlExpr (Update val) # (<#) :: (a -> b) -> SqlExpr (Value a) -> SqlExpr (Insertion b) # (<&>) :: SqlExpr (Insertion (a -> b)) -> SqlExpr (Value a) -> SqlExpr (Insertion b) # case_ :: PersistField a => [(SqlExpr (Value Bool), SqlExpr (Value a))] -> SqlExpr (Value a) -> SqlExpr (Value a) # toBaseId :: ToBaseId ent => SqlExpr (Value (Key ent)) -> SqlExpr (Value (Key (BaseEnt ent))) #

data SqlExpr a #

An expression on the SQL backend.

There are many comments describing the constructors of this data type. However, Haddock doesn't like GADTs, so you'll have to read them by hitting "Source".

Instances

Esqueleto SqlQuery SqlExpr SqlBackend # |
Methods fromStart :: (PersistEntity a, (* ~ PersistEntityBackend a) SqlBackend) => SqlQuery (SqlExpr (PreprocessedFrom (SqlExpr (Entity a)))) # fromStartMaybe :: (PersistEntity a, (* ~ PersistEntityBackend a) SqlBackend) => SqlQuery (SqlExpr (PreprocessedFrom (SqlExpr (Maybe (Entity a))))) # fromJoin :: IsJoinKind join => SqlExpr (PreprocessedFrom a) -> SqlExpr (PreprocessedFrom b) -> SqlQuery (SqlExpr (PreprocessedFrom (join a b))) # fromFinish :: SqlExpr (PreprocessedFrom a) -> SqlQuery a # where_ :: SqlExpr (Value Bool) -> SqlQuery () # on :: SqlExpr (Value Bool) -> SqlQuery () # groupBy :: ToSomeValues SqlExpr a => a -> SqlQuery () # orderBy :: [SqlExpr OrderBy] -> SqlQuery () # asc :: PersistField a => SqlExpr (Value a) -> SqlExpr OrderBy # desc :: PersistField a => SqlExpr (Value a) -> SqlExpr OrderBy # limit :: Int64 -> SqlQuery () # offset :: Int64 -> SqlQuery () # distinct :: SqlQuery a -> SqlQuery a # distinctOn :: [SqlExpr DistinctOn] -> SqlQuery a -> SqlQuery a # don :: SqlExpr (Value a) -> SqlExpr DistinctOn # distinctOnOrderBy :: [SqlExpr OrderBy] -> SqlQuery a -> SqlQuery a # rand :: SqlExpr OrderBy # having :: SqlExpr (Value Bool) -> SqlQuery () # locking :: LockingKind -> SqlQuery () # sub_select :: PersistField a => SqlQuery (SqlExpr (Value a)) -> SqlExpr (Value a) # sub_selectDistinct :: PersistField a => SqlQuery (SqlExpr (Value a)) -> SqlExpr (Value a) # (^.) :: (PersistEntity val, PersistField typ) => SqlExpr (Entity val) -> EntityField val typ -> SqlExpr (Value typ) # (?.) :: (PersistEntity val, PersistField typ) => SqlExpr (Maybe (Entity val)) -> EntityField val typ -> SqlExpr (Value (Maybe typ)) # val :: PersistField typ => typ -> SqlExpr (Value typ) # isNothing :: PersistField typ => SqlExpr (Value (Maybe typ)) -> SqlExpr (Value Bool) # just :: SqlExpr (Value typ) -> SqlExpr (Value (Maybe typ)) # nothing :: SqlExpr (Value (Maybe typ)) # joinV :: SqlExpr (Value (Maybe (Maybe typ))) -> SqlExpr (Value (Maybe typ)) # countRows :: Num a => SqlExpr (Value a) # count :: Num a => SqlExpr (Value typ) -> SqlExpr (Value a) # countDistinct :: Num a => SqlExpr (Value typ) -> SqlExpr (Value a) # not_ :: SqlExpr (Value Bool) -> SqlExpr (Value Bool) # (==.) :: PersistField typ => SqlExpr (Value typ) -> SqlExpr (Value typ) -> SqlExpr (Value Bool) # (>=.) :: PersistField typ => SqlExpr (Value typ) -> SqlExpr (Value typ) -> SqlExpr (Value Bool) # (>.) :: PersistField typ => SqlExpr (Value typ) -> SqlExpr (Value typ) -> SqlExpr (Value Bool) # (<=.) :: PersistField typ => SqlExpr (Value typ) -> SqlExpr (Value typ) -> SqlExpr (Value Bool) # (<.) :: PersistField typ => SqlExpr (Value typ) -> SqlExpr (Value typ) -> SqlExpr (Value Bool) # (!=.) :: PersistField typ => SqlExpr (Value typ) -> SqlExpr (Value typ) -> SqlExpr (Value Bool) # (&&.) :: SqlExpr (Value Bool) -> SqlExpr (Value Bool) -> SqlExpr (Value Bool) # (||.) :: SqlExpr (Value Bool) -> SqlExpr (Value Bool) -> SqlExpr (Value Bool) # (+.) :: PersistField a => SqlExpr (Value a) -> SqlExpr (Value a) -> SqlExpr (Value a) # (-.) :: PersistField a => SqlExpr (Value a) -> SqlExpr (Value a) -> SqlExpr (Value a) # (/.) :: PersistField a => SqlExpr (Value a) -> SqlExpr (Value a) -> SqlExpr (Value a) # (*.) :: PersistField a => SqlExpr (Value a) -> SqlExpr (Value a) -> SqlExpr (Value a) # random_ :: (PersistField a, Num a) => SqlExpr (Value a) # round_ :: (PersistField a, Num a, PersistField b, Num b) => SqlExpr (Value a) -> SqlExpr (Value b) # ceiling_ :: (PersistField a, Num a, PersistField b, Num b) => SqlExpr (Value a) -> SqlExpr (Value b) # floor_ :: (PersistField a, Num a, PersistField b, Num b) => SqlExpr (Value a) -> SqlExpr (Value b) # sum_ :: (PersistField a, PersistField b) => SqlExpr (Value a) -> SqlExpr (Value (Maybe b)) # min_ :: PersistField a => SqlExpr (Value a) -> SqlExpr (Value (Maybe a)) # max_ :: PersistField a => SqlExpr (Value a) -> SqlExpr (Value (Maybe a)) # avg_ :: (PersistField a, PersistField b) => SqlExpr (Value a) -> SqlExpr (Value (Maybe b)) # castNum :: (Num a, Num b) => SqlExpr (Value a) -> SqlExpr (Value b) # castNumM :: (Num a, Num b) => SqlExpr (Value (Maybe a)) -> SqlExpr (Value (Maybe b)) # coalesce :: PersistField a => [SqlExpr (Value (Maybe a))] -> SqlExpr (Value (Maybe a)) # coalesceDefault :: PersistField a => [SqlExpr (Value (Maybe a))] -> SqlExpr (Value a) -> SqlExpr (Value a) # lower_ :: SqlString s => SqlExpr (Value s) -> SqlExpr (Value s) # like :: SqlString s => SqlExpr (Value s) -> SqlExpr (Value s) -> SqlExpr (Value Bool) # ilike :: SqlString s => SqlExpr (Value s) -> SqlExpr (Value s) -> SqlExpr (Value Bool) # (%) :: SqlString s => SqlExpr (Value s) # concat_ :: SqlString s => [SqlExpr (Value s)] -> SqlExpr (Value s) # (++.) :: SqlString s => SqlExpr (Value s) -> SqlExpr (Value s) -> SqlExpr (Value s) # castString :: (SqlString s, SqlString r) => SqlExpr (Value s) -> SqlExpr (Value r) # subList_select :: PersistField a => SqlQuery (SqlExpr (Value a)) -> SqlExpr (ValueList a) # subList_selectDistinct :: PersistField a => SqlQuery (SqlExpr (Value a)) -> SqlExpr (ValueList a) # valList :: PersistField typ => [typ] -> SqlExpr (ValueList typ) # justList :: SqlExpr (ValueList typ) -> SqlExpr (ValueList (Maybe typ)) # in_ :: PersistField typ => SqlExpr (Value typ) -> SqlExpr (ValueList typ) -> SqlExpr (Value Bool) # notIn :: PersistField typ => SqlExpr (Value typ) -> SqlExpr (ValueList typ) -> SqlExpr (Value Bool) # exists :: SqlQuery () -> SqlExpr (Value Bool) # notExists :: SqlQuery () -> SqlExpr (Value Bool) # set :: PersistEntity val => SqlExpr (Entity val) -> [SqlExpr (Update val)] -> SqlQuery () # (=.) :: (PersistEntity val, PersistField typ) => EntityField val typ -> SqlExpr (Value typ) -> SqlExpr (Update val) # (+=.) :: (PersistEntity val, PersistField a) => EntityField val a -> SqlExpr (Value a) -> SqlExpr (Update val) # (-=.) :: (PersistEntity val, PersistField a) => EntityField val a -> SqlExpr (Value a) -> SqlExpr (Update val) # (*=.) :: (PersistEntity val, PersistField a) => EntityField val a -> SqlExpr (Value a) -> SqlExpr (Update val) # (/=.) :: (PersistEntity val, PersistField a) => EntityField val a -> SqlExpr (Value a) -> SqlExpr (Update val) # (<#) :: (a -> b) -> SqlExpr (Value a) -> SqlExpr (Insertion b) # (<&>) :: SqlExpr (Insertion (a -> b)) -> SqlExpr (Value a) -> SqlExpr (Insertion b) # case_ :: PersistField a => [(SqlExpr (Value Bool), SqlExpr (Value a))] -> SqlExpr (Value a) -> SqlExpr (Value a) # toBaseId :: ToBaseId ent => SqlExpr (Value (Key ent)) -> SqlExpr (Value (Key (BaseEnt ent))) #
ToSomeValues SqlExpr (SqlExpr (Value a)) # |
Methods toSomeValues :: SqlExpr (Value a) -> [SomeValue SqlExpr] #
(~) * a (Value b) => UnsafeSqlFunctionArgument (SqlExpr a) # |
Methods toArgList :: SqlExpr a -> [SqlExpr (Value ())]
PersistEntity a => SqlSelect (SqlExpr (Maybe (Entity a))) (Maybe (Entity a)) # | You may return a possibly-`NULL` `Entity` from a `select` query.
Methods sqlSelectCols :: IdentInfo -> SqlExpr (Maybe (Entity a)) -> (Builder, [PersistValue]) # sqlSelectColCount :: Proxy * (SqlExpr (Maybe (Entity a))) -> Int # sqlSelectProcessRow :: [PersistValue] -> Either Text (Maybe (Entity a)) # sqlInsertInto :: IdentInfo -> SqlExpr (Maybe (Entity a)) -> (Builder, [PersistValue]) #
PersistEntity a => SqlSelect (SqlExpr (Entity a)) (Entity a) # | You may return an `Entity` from a `select` query.
Methods sqlSelectCols :: IdentInfo -> SqlExpr (Entity a) -> (Builder, [PersistValue]) # sqlSelectColCount :: Proxy * (SqlExpr (Entity a)) -> Int # sqlSelectProcessRow :: [PersistValue] -> Either Text (Entity a) # sqlInsertInto :: IdentInfo -> SqlExpr (Entity a) -> (Builder, [PersistValue]) #
PersistField a => SqlSelect (SqlExpr (Value a)) (Value a) # | You may return any single value (i.e. a single column) from a `select` query.
Methods sqlSelectCols :: IdentInfo -> SqlExpr (Value a) -> (Builder, [PersistValue]) # sqlSelectColCount :: Proxy * (SqlExpr (Value a)) -> Int # sqlSelectProcessRow :: [PersistValue] -> Either Text (Value a) # sqlInsertInto :: IdentInfo -> SqlExpr (Value a) -> (Builder, [PersistValue]) #

type SqlEntity ent = (PersistEntity ent, PersistEntityBackend ent ~ SqlBackend) #

Constraint synonym for `persistent` entities whose backend is `SqlPersistT`.

select :: (SqlSelect a r, MonadIO m) => SqlQuery a -> SqlReadT m [r] #

Execute an `esqueleto` `SELECT` query inside `persistent`'s `SqlPersistT` monad and return a list of rows.

We've seen that `from` has some magic about which kinds of things you may bring into scope. This `select` function also has some magic for which kinds of things you may bring back to Haskell-land by using `SqlQuery`'s `return`:

- You may return a `SqlExpr (`Entity` v)` for an entity `v` (i.e., like the `*` in SQL), which is then returned to Haskell-land as just `Entity v`.
- You may return a `SqlExpr (Maybe (Entity v))` for an entity `v` that may be `NULL`, which is then returned to Haskell-land as `Maybe (Entity v)`. Used for `OUTER JOIN`s.
- You may return a `SqlExpr (`Value` t)` for a value `t` (i.e., a single column), where `t` is any instance of `PersistField`, which is then returned to Haskell-land as `Value t`. You may use `Value` to return projections of an `Entity` (see `(`^.`)` and `(`?.`)`) or to return any other value calculated on the query (e.g., `countRows` or `sub_select`).

The `SqlSelect a r` class has functional dependencies that allow type information to flow both from `a` to `r` and vice-versa. This means that you'll almost never have to give any type signatures for `esqueleto` queries. For example, the query ``select` $ from $ \p -> return p` alone is ambiguous, but in the context of

    do ps <- select $
             from $ \p ->
             return p
       liftIO $ mapM_ (putStrLn . personName . entityVal) ps

we are able to infer from that single `personName . entityVal` function composition that the `p` inside the query is of type `SqlExpr (Entity Person)`.

selectDistinct :: (SqlSelect a r, MonadIO m) => SqlQuery a -> SqlPersistT m [r] #

Deprecated: Since 2.2.4: use `select` and `distinct`.

Execute an `esqueleto` `SELECT DISTINCT` query inside `persistent`'s `SqlPersistT` monad and return a list of rows.

selectSource :: (SqlSelect a r, MonadResource m) => SqlQuery a -> Source (SqlPersistT m) r #

Execute an `esqueleto` `SELECT` query inside `persistent`'s `SqlPersistT` monad and return a `Source` of rows.

selectDistinctSource :: (SqlSelect a r, MonadResource m) => SqlQuery a -> Source (SqlPersistT m) r #

Deprecated: Since 2.2.4: use `selectSource` and `distinct`.

Execute an `esqueleto` `SELECT DISTINCT` query inside `persistent`'s `SqlPersistT` monad and return a `Source` of rows.

delete :: MonadIO m => SqlQuery () -> SqlWriteT m () #

Execute an `esqueleto` `DELETE` query inside `persistent`'s `SqlPersistT` monad. Note that currently there are no type checks for statements that should not appear on a `DELETE` query.

Example of usage:

    delete $
    from $ \appointment ->
    where_ (appointment ^. AppointmentDate <. val now)

Unlike `select`, there is a useful way of using `delete` that will lead to type ambiguities. If you want to delete all rows (i.e., no `where_` clause), you'll have to use a type signature:

    delete $
    from $ \(appointment :: SqlExpr (Entity Appointment)) ->
    return ()

deleteCount :: MonadIO m => SqlQuery () -> SqlWriteT m Int64 #

Same as `delete`, but returns the number of rows affected.

update :: (MonadIO m, SqlEntity val) => (SqlExpr (Entity val) -> SqlQuery ()) -> SqlWriteT m () #

Execute an `esqueleto` `UPDATE` query inside `persistent`'s `SqlPersistT` monad. Note that currently there are no type checks for statements that should not appear on a `UPDATE` query.

Example of usage:

    update $ \p -> do
    set p [ PersonAge =. just (val thisYear) -. p ^. PersonBorn ]
    where_ $ isNothing (p ^. PersonAge)

updateCount :: (MonadIO m, SqlEntity val) => (SqlExpr (Entity val) -> SqlQuery ()) -> SqlWriteT m Int64 #

Same as `update`, but returns the number of rows affected.

insertSelect :: (MonadIO m, PersistEntity a) => SqlQuery (SqlExpr (Insertion a)) -> SqlWriteT m () #

Insert a `PersistField` for every selected value.

Since: 2.4.2

insertSelectCount :: (MonadIO m, PersistEntity a) => SqlQuery (SqlExpr (Insertion a)) -> SqlWriteT m Int64 #

Insert a `PersistField` for every selected value, return the count afterward

insertSelectDistinct :: (MonadIO m, PersistEntity a) => SqlQuery (SqlExpr (Insertion a)) -> SqlWriteT m () #

Deprecated: Since 2.2.4: use `insertSelect` and `distinct`.

Insert a `PersistField` for every unique selected value.

(<#) :: Esqueleto query expr backend => (a -> b) -> expr (Value a) -> expr (Insertion b) #

Apply a `PersistField` constructor to `expr Value` arguments.

(<&>) :: Esqueleto query expr backend => expr (Insertion (a -> b)) -> expr (Value a) -> expr (Insertion b) #

Apply extra `expr Value` arguments to a `PersistField` constructor

# RDBMS-specific modules

There are many differences between SQL syntax and functions supported by different RDBMSs. Since version 2.2.8, `esqueleto` includes modules containing functions that are specific to a given RDBMS.

- PostgreSQL: Database.Esqueleto.PostgreSQL.

In order to use these functions, you need to explicitly import their corresponding modules, they're not re-exported here.

# Helpers

valkey :: (Esqueleto query expr backend, ToBackendKey SqlBackend entity, PersistField (Key entity)) => Int64 -> expr (Value (Key entity)) #

`valkey i = `val` . `toSqlKey`` (https://github.com/prowdsponsor/esqueleto/issues/9).

valJ :: (Esqueleto query expr backend, PersistField (Key entity)) => Value (Key entity) -> expr (Value (Key entity)) #

`valJ` is like `val` but for something that is already a `Value`. The use case it was written for was, given a `Value` lift the `Key` for that `Value` into the query expression in a type safe way. However, the implementation is more generic than that so we call it `valJ`.

Its important to note that the input entity and the output entity are constrained to be the same by the type signature on the function (https://github.com/prowdsponsor/esqueleto/pull/69).

Since: 1.4.2

# Re-exports

We re-export many symbols from `persistent` for convenince:

- "Store functions" from Database.Persist.
- Everything from Database.Persist.Class except for `PersistQuery` and `delete` (use `deleteKey` instead).
- Everything from Database.Persist.Types except for `Update`, `SelectOpt`, `BackendSpecificFilter` and `Filter`.
- Everything from Database.Persist.Sql except for `deleteWhereCount` and `updateWhereCount`.

deleteKey :: (PersistStore backend, BaseBackend backend ~ PersistEntityBackend val, MonadIO m, PersistEntity val) => Key val -> ReaderT backend m () #

Synonym for `delete` that does not clash with `esqueleto`'s `delete`.

module Database.Persist.Sql