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

Safe Haskell | None
Language | Haskell98

Database.Esqueleto.Internal.Language

Contents

- The pretty face
- The guts

Description

This is an internal module, anything exported by this module may change without a major version bump. Please use only Database.Esqueleto if possible.

Synopsis

- class (Functor query, Applicative query, Monad query) => Esqueleto query expr backend | query -> expr backend, expr -> query backend where
- 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 SomeValue expr where
  - SomeValue :: Esqueleto query expr backend => expr (Value a) -> SomeValue expr
- class ToSomeValues expr a where
- 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 OrderBy
- data DistinctOn
- data Update typ
- data Insertion a
- data LockingKind
  - = ForUpdate
  - | ForShare
  - | LockInShareMode
- class PersistField a => SqlString a
- class ToBaseId ent where
  - type BaseEnt ent :: *
- data JoinKind
  - = InnerJoinKind
  - | CrossJoinKind
  - | LeftOuterJoinKind
  - | RightOuterJoinKind
  - | FullOuterJoinKind
- class IsJoinKind join where
- data PreprocessedFrom a
- class Esqueleto query expr backend => From query expr backend a
- class Esqueleto query expr backend => FromPreprocess query expr backend a
- when_ :: expr (Value Bool) -> () -> expr a -> (expr (Value Bool), expr a)
- then_ :: ()
- else_ :: expr a -> expr a

# The pretty face

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

fromStart :: (PersistEntity a, PersistEntityBackend a ~ backend) => query (expr (PreprocessedFrom (expr (Entity a)))) #

(Internal) Start a `from` query with an entity. `from` does two kinds of magic using `fromStart`, `fromJoin` and `fromFinish`:

1. The simple but tedious magic of allowing tuples to be used.
2. The more advanced magic of creating `JOIN`s. The `JOIN` is processed from right to left. The rightmost entity of the `JOIN` is created with `fromStart`. Each `JOIN` step is then translated into a call to `fromJoin`. In the end, `fromFinish` is called to materialize the `JOIN`.

fromStartMaybe :: (PersistEntity a, PersistEntityBackend a ~ backend) => query (expr (PreprocessedFrom (expr (Maybe (Entity a))))) #

(Internal) Same as `fromStart`, but entity may be missing.

fromJoin :: IsJoinKind join => expr (PreprocessedFrom a) -> expr (PreprocessedFrom b) -> query (expr (PreprocessedFrom (join a b))) #

(Internal) Do a `JOIN`.

fromFinish :: expr (PreprocessedFrom a) -> query a #

(Internal) Finish a `JOIN`.

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))) #

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 SomeValue expr where #

A wrapper type for for any `expr (Value a)` for all a.

Constructors

SomeValue :: Esqueleto query expr backend => expr (Value a) -> SomeValue expr |

class ToSomeValues expr a where #

A class of things that can be converted into a list of SomeValue. It has instances for tuples and is the reason why `groupBy` can take tuples, like ``groupBy` (foo `^.` FooId, foo `^.` FooName, foo `^.` FooType)`.

Minimal complete definition

toSomeValues

Methods

toSomeValues :: a -> [SomeValue expr] #

Instances

ToSomeValues SqlExpr (SqlExpr (Value a)) # |
Methods toSomeValues :: SqlExpr (Value a) -> [SomeValue SqlExpr] #
(ToSomeValues expr a, ToSomeValues expr b) => ToSomeValues expr (a, b) # |
Methods toSomeValues :: (a, b) -> [SomeValue expr] #
(ToSomeValues expr a, ToSomeValues expr b, ToSomeValues expr c) => ToSomeValues expr (a, b, c) # |
Methods toSomeValues :: (a, b, c) -> [SomeValue expr] #
(ToSomeValues expr a, ToSomeValues expr b, ToSomeValues expr c, ToSomeValues expr d) => ToSomeValues expr (a, b, c, d) # |
Methods toSomeValues :: (a, b, c, d) -> [SomeValue expr] #
(ToSomeValues expr a, ToSomeValues expr b, ToSomeValues expr c, ToSomeValues expr d, ToSomeValues expr e) => ToSomeValues expr (a, b, c, d, e) # |
Methods toSomeValues :: (a, b, c, d, e) -> [SomeValue expr] #
(ToSomeValues expr a, ToSomeValues expr b, ToSomeValues expr c, ToSomeValues expr d, ToSomeValues expr e, ToSomeValues expr f) => ToSomeValues expr (a, b, c, d, e, f) # |
Methods toSomeValues :: (a, b, c, d, e, f) -> [SomeValue expr] #
(ToSomeValues expr a, ToSomeValues expr b, ToSomeValues expr c, ToSomeValues expr d, ToSomeValues expr e, ToSomeValues expr f, ToSomeValues expr g) => ToSomeValues expr (a, b, c, d, e, f, g) # |
Methods toSomeValues :: (a, b, c, d, e, f, g) -> [SomeValue expr] #
(ToSomeValues expr a, ToSomeValues expr b, ToSomeValues expr c, ToSomeValues expr d, ToSomeValues expr e, ToSomeValues expr f, ToSomeValues expr g, ToSomeValues expr h) => ToSomeValues expr (a, b, c, d, e, f, g, h) # |
Methods toSomeValues :: (a, b, c, d, e, f, g, h) -> [SomeValue expr] #

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 #

data OrderBy #

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

data DistinctOn #

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

data Update typ #

Phantom type for a `SET` operation on an entity of the given type (see `set` and '(=.)').

data Insertion a #

Phantom type used by `insertSelect`.

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

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 #

# The guts

data JoinKind #

(Internal) A kind of `JOIN`.

Constructors

InnerJoinKind |
    INNER JOIN
CrossJoinKind |
    CROSS JOIN
LeftOuterJoinKind |
    LEFT OUTER JOIN
RightOuterJoinKind |
    RIGHT OUTER JOIN
FullOuterJoinKind |
    FULL OUTER JOIN

Instances

Eq JoinKind # |
Methods (==) :: JoinKind -> JoinKind -> Bool # (/=) :: JoinKind -> JoinKind -> Bool #

class IsJoinKind join where #

(Internal) Functions that operate on types (that should be) of kind `JoinKind`.

Minimal complete definition

smartJoin, reifyJoinKind

Methods

smartJoin :: a -> b -> join a b #

(Internal) `smartJoin a b` is a `JOIN` of the correct kind.

reifyJoinKind :: join a b -> JoinKind #

(Internal) Reify a `JoinKind` from a `JOIN`. This function is non-strict.

Instances

IsJoinKind FullOuterJoin # |
Methods smartJoin :: a -> b -> FullOuterJoin a b # reifyJoinKind :: FullOuterJoin a b -> JoinKind #
IsJoinKind RightOuterJoin # |
Methods smartJoin :: a -> b -> RightOuterJoin a b # reifyJoinKind :: RightOuterJoin a b -> JoinKind #
IsJoinKind LeftOuterJoin # |
Methods smartJoin :: a -> b -> LeftOuterJoin a b # reifyJoinKind :: LeftOuterJoin a b -> JoinKind #
IsJoinKind CrossJoin # |
Methods smartJoin :: a -> b -> CrossJoin a b # reifyJoinKind :: CrossJoin a b -> JoinKind #
IsJoinKind InnerJoin # |
Methods smartJoin :: a -> b -> InnerJoin a b # reifyJoinKind :: InnerJoin a b -> JoinKind #

data PreprocessedFrom a #

(Internal) Phantom type used to process `from` (see `fromStart`).

class Esqueleto query expr backend => From query expr backend a #

(Internal) Class that implements the tuple `from` magic (see `fromStart`).

Minimal complete definition

from_

Instances

(Esqueleto query expr backend, FromPreprocess query expr backend (expr (Maybe (Entity val)))) => From query expr backend (expr (Maybe (Entity val))) # |
Methods from_ :: query (expr (Maybe (Entity val)))
(Esqueleto query expr backend, FromPreprocess query expr backend (expr (Entity val))) => From query expr backend (expr (Entity val)) # |
Methods from_ :: query (expr (Entity val))
(From query expr backend a, From query expr backend b) => From query expr backend (a, b) # |
Methods from_ :: query (a, b)
(Esqueleto query expr backend, FromPreprocess query expr backend (FullOuterJoin a b)) => From query expr backend (FullOuterJoin a b) # |
Methods from_ :: query (FullOuterJoin a b)
(Esqueleto query expr backend, FromPreprocess query expr backend (RightOuterJoin a b)) => From query expr backend (RightOuterJoin a b) # |
Methods from_ :: query (RightOuterJoin a b)
(Esqueleto query expr backend, FromPreprocess query expr backend (LeftOuterJoin a b)) => From query expr backend (LeftOuterJoin a b) # |
Methods from_ :: query (LeftOuterJoin a b)
(Esqueleto query expr backend, FromPreprocess query expr backend (CrossJoin a b)) => From query expr backend (CrossJoin a b) # |
Methods from_ :: query (CrossJoin a b)
(Esqueleto query expr backend, FromPreprocess query expr backend (InnerJoin a b)) => From query expr backend (InnerJoin a b) # |
Methods from_ :: query (InnerJoin a b)
(From query expr backend a, From query expr backend b, From query expr backend c) => From query expr backend (a, b, c) # |
Methods from_ :: query (a, b, c)
(From query expr backend a, From query expr backend b, From query expr backend c, From query expr backend d) => From query expr backend (a, b, c, d) # |
Methods from_ :: query (a, b, c, d)
(From query expr backend a, From query expr backend b, From query expr backend c, From query expr backend d, From query expr backend e) => From query expr backend (a, b, c, d, e) # |
Methods from_ :: query (a, b, c, d, e)
(From query expr backend a, From query expr backend b, From query expr backend c, From query expr backend d, From query expr backend e, From query expr backend f) => From query expr backend (a, b, c, d, e, f) # |
Methods from_ :: query (a, b, c, d, e, f)
(From query expr backend a, From query expr backend b, From query expr backend c, From query expr backend d, From query expr backend e, From query expr backend f, From query expr backend g) => From query expr backend (a, b, c, d, e, f, g) # |
Methods from_ :: query (a, b, c, d, e, f, g)
(From query expr backend a, From query expr backend b, From query expr backend c, From query expr backend d, From query expr backend e, From query expr backend f, From query expr backend g, From query expr backend h) => From query expr backend (a, b, c, d, e, f, g, h) # |
Methods from_ :: query (a, b, c, d, e, f, g, h)

class Esqueleto query expr backend => FromPreprocess query expr backend a #

(Internal) Class that implements the `JOIN` `from` magic (see `fromStart`).

Minimal complete definition

fromPreprocess

Instances

(Esqueleto query expr backend, PersistEntity val, (~) * (PersistEntityBackend val) backend) => FromPreprocess query expr backend (expr (Maybe (Entity val))) # |
Methods fromPreprocess :: query (expr (PreprocessedFrom (expr (Maybe (Entity val)))))
(Esqueleto query expr backend, PersistEntity val, (~) * (PersistEntityBackend val) backend) => FromPreprocess query expr backend (expr (Entity val)) # |
Methods fromPreprocess :: query (expr (PreprocessedFrom (expr (Entity val))))
(Esqueleto query expr backend, FromPreprocess query expr backend a, FromPreprocess query expr backend b, IsJoinKind join) => FromPreprocess query expr backend (join a b) # |
Methods fromPreprocess :: query (expr (PreprocessedFrom (join a b)))

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