esqueleto-1.3.4.2: Bare bones, type-safe EDSL for SQL queries on persistent backends.

Safe Haskell | None

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
  - fromStart :: (PersistEntity a, PersistEntityBackend a ~ backend) => query (expr (PreprocessedFrom (expr (Entity a))))
  - fromStartMaybe :: (PersistEntity a, PersistEntityBackend a ~ backend) => query (expr (PreprocessedFrom (expr (Maybe (Entity a)))))
  - fromJoin :: IsJoinKind join => expr (PreprocessedFrom a) -> expr (PreprocessedFrom b) -> query (expr (PreprocessedFrom (join a b)))
  - fromFinish :: expr (PreprocessedFrom a) -> query a
  - where_ :: expr (Value Bool) -> query ()
  - on :: expr (Value Bool) -> query ()
  - groupBy :: ToSomeValues expr a => a -> query ()
  - orderBy :: [expr OrderBy] -> query ()
  - asc :: PersistField a => expr (Value a) -> expr OrderBy
  - desc :: PersistField a => expr (Value a) -> expr OrderBy
  - limit :: Int64 -> query ()
  - offset :: Int64 -> query ()
  - having :: expr (Value Bool) -> query ()
  - sub_select :: PersistField a => query (expr (Value a)) -> expr (Value a)
  - sub_selectDistinct :: PersistField a => query (expr (Value a)) -> expr (Value a)
  - (^.) :: (PersistEntity val, PersistField typ) => expr (Entity val) -> EntityField val typ -> expr (Value typ)
  - (?.) :: (PersistEntity val, PersistField typ) => expr (Maybe (Entity val)) -> EntityField val typ -> expr (Value (Maybe typ))
  - val :: PersistField typ => typ -> expr (Value typ)
  - isNothing :: PersistField typ => expr (Value (Maybe typ)) -> expr (Value Bool)
  - just :: expr (Value typ) -> expr (Value (Maybe typ))
  - nothing :: expr (Value (Maybe typ))
  - joinV :: expr (Value (Maybe (Maybe typ))) -> expr (Value (Maybe typ))
  - countRows :: Num a => expr (Value a)
  - count :: Num a => expr (Value typ) -> expr (Value a)
  - not_ :: expr (Value Bool) -> expr (Value Bool)
  - (==.) :: PersistField typ => expr (Value typ) -> expr (Value typ) -> expr (Value Bool)
  - (>=.) :: PersistField typ => expr (Value typ) -> expr (Value typ) -> expr (Value Bool)
  - (>.) :: PersistField typ => expr (Value typ) -> expr (Value typ) -> expr (Value Bool)
  - (<=.) :: PersistField typ => expr (Value typ) -> expr (Value typ) -> expr (Value Bool)
  - (<.) :: PersistField typ => expr (Value typ) -> expr (Value typ) -> expr (Value Bool)
  - (!=.) :: PersistField typ => expr (Value typ) -> expr (Value typ) -> expr (Value Bool)
  - (&&.) :: expr (Value Bool) -> expr (Value Bool) -> expr (Value Bool)
  - (||.) :: expr (Value Bool) -> expr (Value Bool) -> expr (Value Bool)
  - (+.) :: PersistField a => expr (Value a) -> expr (Value a) -> expr (Value a)
  - (-.) :: PersistField a => expr (Value a) -> expr (Value a) -> expr (Value a)
  - (/.) :: PersistField a => expr (Value a) -> expr (Value a) -> expr (Value a)
  - (*.) :: PersistField a => expr (Value a) -> expr (Value a) -> expr (Value a)
  - random_ :: PersistField a => expr (Value a)
  - round_ :: (PersistField a, PersistField b) => expr (Value a) -> expr (Value b)
  - ceiling_ :: (PersistField a, PersistField b) => expr (Value a) -> expr (Value b)
  - floor_ :: (PersistField a, PersistField b) => expr (Value a) -> expr (Value b)
  - sum_ :: PersistField a => expr (Value a) -> expr (Value (Maybe a))
  - 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))
  - like :: (PersistField s, IsString s) => expr (Value s) -> expr (Value s) -> expr (Value Bool)
  - (%) :: (PersistField s, IsString s) => expr (Value s)
  - concat_ :: (PersistField s, IsString s) => [expr (Value s)] -> expr (Value s)
  - (++.) :: (PersistField s, IsString s) => expr (Value s) -> expr (Value s) -> expr (Value s)
  - subList_select :: PersistField a => query (expr (Value a)) -> expr (ValueList a)
  - subList_selectDistinct :: PersistField a => query (expr (Value a)) -> expr (ValueList a)
  - valList :: PersistField typ => [typ] -> expr (ValueList typ)
  - in_ :: PersistField typ => expr (Value typ) -> expr (ValueList typ) -> expr (Value Bool)
  - notIn :: PersistField typ => expr (Value typ) -> expr (ValueList typ) -> expr (Value Bool)
  - exists :: query () -> expr (Value Bool)
  - notExists :: query () -> expr (Value Bool)
  - set :: PersistEntity val => expr (Entity val) -> [expr (Update val)] -> query ()
  - (=.) :: (PersistEntity val, PersistField typ) => EntityField val typ -> expr (Value typ) -> expr (Update val)
  - (+=.) :: (PersistEntity val, PersistField a) => EntityField val a -> expr (Value a) -> expr (Update val)
  - (-=.) :: (PersistEntity val, PersistField a) => EntityField val a -> expr (Value a) -> expr (Update val)
  - (*=.) :: (PersistEntity val, PersistField a) => EntityField val a -> expr (Value a) -> expr (Update val)
  - (/=.) :: (PersistEntity val, PersistField a) => EntityField val a -> expr (Value a) -> expr (Update val)
  - (<#) :: (a -> b) -> expr (Value a) -> expr (Insertion b)
  - (<&>) :: expr (Insertion (a -> b)) -> expr (Value a) -> expr (Insertion b)
- from :: From query expr backend a => (a -> query b) -> query b
- data Value a = Value 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
  - toSomeValues :: a -> [SomeValue expr]
- 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 Update typ
- data Insertion a
- data JoinKind
  - = InnerJoinKind
  - | CrossJoinKind
  - | LeftOuterJoinKind
  - | RightOuterJoinKind
  - | FullOuterJoinKind
- class IsJoinKind join where
  - smartJoin :: a -> b -> join a b
  - reifyJoinKind :: join a b -> JoinKind
- data PreprocessedFrom a
- class Esqueleto query expr backend => From query expr backend a
- class Esqueleto query expr backend => FromPreprocess query expr backend a

# The pretty face

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

Finally tagless representation of `esqueleto`'s EDSL.

Methods

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

(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)))))Source

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

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

(Internal) Do a `JOIN`.

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

(Internal) Finish a `JOIN`.

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

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

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

`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 ()Source

`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):

     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 ()Source

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

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

Ascending order of this field or expression.

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

Descending order of this field or expression.

limit :: Int64 -> query ()Source

`LIMIT`. Limit the number of returned rows.

offset :: Int64 -> query ()Source

`OFFSET`. Usually used with `limit`.

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

`HAVING`.

Since: 1.2.2

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

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)Source

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

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

Project a field of an entity.

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

Project a field of an entity that may be null.

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

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

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

`IS NULL` comparison.

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

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))Source

`NULL` value.

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

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)Source

`COUNT(*)` value.

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

`COUNT`.

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

(==.) :: PersistField typ => expr (Value typ) -> expr (Value typ) -> expr (Value Bool)Source

(>=.) :: PersistField typ => expr (Value typ) -> expr (Value typ) -> expr (Value Bool)Source

(>.) :: PersistField typ => expr (Value typ) -> expr (Value typ) -> expr (Value Bool)Source

(<=.) :: PersistField typ => expr (Value typ) -> expr (Value typ) -> expr (Value Bool)Source

(<.) :: PersistField typ => expr (Value typ) -> expr (Value typ) -> expr (Value Bool)Source

(!=.) :: PersistField typ => expr (Value typ) -> expr (Value typ) -> expr (Value Bool)Source

(&&.) :: expr (Value Bool) -> expr (Value Bool) -> expr (Value Bool)Source

(||.) :: expr (Value Bool) -> expr (Value Bool) -> expr (Value Bool)Source

(+.) :: PersistField a => expr (Value a) -> expr (Value a) -> expr (Value a)Source

(-.) :: PersistField a => expr (Value a) -> expr (Value a) -> expr (Value a)Source

(/.) :: PersistField a => expr (Value a) -> expr (Value a) -> expr (Value a)Source

(*.) :: PersistField a => expr (Value a) -> expr (Value a) -> expr (Value a)Source

random_ :: PersistField a => expr (Value a)Source

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

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

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

sum_ :: PersistField a => expr (Value a) -> expr (Value (Maybe a))Source

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

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

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

like :: (PersistField s, IsString s) => expr (Value s) -> expr (Value s) -> expr (Value Bool)Source

`LIKE` operator.

(%) :: (PersistField s, IsString s) => expr (Value s)Source

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

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

concat_ :: (PersistField s, IsString s) => [expr (Value s)] -> expr (Value s)Source

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

(++.) :: (PersistField s, IsString s) => expr (Value s) -> expr (Value s) -> expr (Value s)Source

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

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

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

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

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

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

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

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

`IN` operator.

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

`NOT IN` operator.

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

`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)Source

`NOT EXISTS` operator.

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

`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)Source

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

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

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

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

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

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

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

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

Instances

Esqueleto SqlQuery SqlExpr SqlBackend |

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

`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 right fixity, the same as in SQL.

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
                     (expr (Entity Person))
                     (InnerJoin (expr (Entity Follow))
                                (expr (Entity Person)))
     ((p1 `InnerJoin` f) `InnerJoin` p2) ::
       :: (...) => InnerJoin
                     (InnerJoin (expr (Entity Person))
                                (expr (Entity Follow)))
                     (expr (Entity Person))

Note that some backends may not support all kinds of `JOIN`s. For example, when using the SQL backend with SQLite, it will not accept the last example above (which is associated to the left, instead of being to the right) and will not accept `RightOuterJoin`s or `FullOuterJoin`s.

data Value a Source

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

Constructors

Value a |

Instances

Typeable1 Value |
ToSomeValues SqlExpr (SqlExpr (Value a)) |
Eq a => Eq (Value a) |
Ord a => Ord (Value a) |
Show a => Show (Value a) |
PersistField a => SqlSelect (SqlExpr (Value a)) (Value a) | You may return any single value (i.e. a single column) from a `select` query.

data ValueList a Source

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

Constructors

ValueList a |

Instances

Typeable1 ValueList |
Eq a => Eq (ValueList a) |
Ord a => Ord (ValueList a) |
Show a => Show (ValueList a) |

data SomeValue expr where Source

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 Source

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)`.

Methods

toSomeValues :: a -> [SomeValue expr]Source

Instances

ToSomeValues SqlExpr (SqlExpr (Value a)) |
(ToSomeValues expr a, ToSomeValues expr b) => ToSomeValues expr (a, b) |
(ToSomeValues expr a, ToSomeValues expr b, ToSomeValues expr c) => ToSomeValues expr (a, b, c) |
(ToSomeValues expr a, ToSomeValues expr b, ToSomeValues expr c, ToSomeValues expr d) => ToSomeValues expr (a, b, c, d) |
(ToSomeValues expr a, ToSomeValues expr b, ToSomeValues expr c, ToSomeValues expr d, ToSomeValues expr e) => ToSomeValues expr (a, b, c, d, e) |
(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) |
(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) |
(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) |

data InnerJoin a b Source

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

Constructors

a InnerJoin b |

Instances

IsJoinKind InnerJoin |
(Esqueleto query expr backend, FromPreprocess query expr backend (InnerJoin a b)) => From query expr backend (InnerJoin a b) |

data CrossJoin a b Source

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

Constructors

a CrossJoin b |

Instances

IsJoinKind CrossJoin |
(Esqueleto query expr backend, FromPreprocess query expr backend (CrossJoin a b)) => From query expr backend (CrossJoin a b) |

data LeftOuterJoin a b Source

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 |

Instances

IsJoinKind LeftOuterJoin |
(Esqueleto query expr backend, FromPreprocess query expr backend (LeftOuterJoin a b)) => From query expr backend (LeftOuterJoin a b) |

data RightOuterJoin a b Source

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

Constructors

a RightOuterJoin b |

Instances

IsJoinKind RightOuterJoin |
(Esqueleto query expr backend, FromPreprocess query expr backend (RightOuterJoin a b)) => From query expr backend (RightOuterJoin a b) |

data FullOuterJoin a b Source

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

Constructors

a FullOuterJoin b |

Instances

IsJoinKind FullOuterJoin |
(Esqueleto query expr backend, FromPreprocess query expr backend (FullOuterJoin a b)) => From query expr backend (FullOuterJoin a b) |

data OnClauseWithoutMatchingJoinException Source

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

Constructors

OnClauseWithoutMatchingJoinException String |

Instances

Eq OnClauseWithoutMatchingJoinException |
Ord OnClauseWithoutMatchingJoinException |
Show OnClauseWithoutMatchingJoinException |
Typeable OnClauseWithoutMatchingJoinException |
Exception OnClauseWithoutMatchingJoinException |

data OrderBy Source

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

data Update typ Source

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

data Insertion a Source

Phantom type used by `insertSelect`.

Instances

PersistEntity a => SqlSelect (SqlExpr (Insertion a)) (Insertion a) | You may return an insertion of some PersistEntity

# The guts

data JoinKind Source

(Internal) A kind of `JOIN`.

Constructors

InnerJoinKind

    INNER JOIN

CrossJoinKind

    CROSS JOIN

LeftOuterJoinKind

    LEFT OUTER JOIN

RightOuterJoinKind

    RIGHT OUTER JOIN

FullOuterJoinKind

    FULL OUTER JOIN

class IsJoinKind join where Source

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

Methods

smartJoin :: a -> b -> join a bSource

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

reifyJoinKind :: join a b -> JoinKind Source

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

Instances

IsJoinKind FullOuterJoin |
IsJoinKind RightOuterJoin |
IsJoinKind LeftOuterJoin |
IsJoinKind CrossJoin |
IsJoinKind InnerJoin |

data PreprocessedFrom a Source

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

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

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

Instances

(Esqueleto query expr backend, FromPreprocess query expr backend (expr (Maybe (Entity val)))) => From query expr backend (expr (Maybe (Entity val))) |
(Esqueleto query expr backend, FromPreprocess query expr backend (expr (Entity val))) => From query expr backend (expr (Entity val)) |
(From query expr backend a, From query expr backend b) => From query expr backend (a, b) |
(Esqueleto query expr backend, FromPreprocess query expr backend (FullOuterJoin a b)) => From query expr backend (FullOuterJoin a b) |
(Esqueleto query expr backend, FromPreprocess query expr backend (RightOuterJoin a b)) => From query expr backend (RightOuterJoin a b) |
(Esqueleto query expr backend, FromPreprocess query expr backend (LeftOuterJoin a b)) => From query expr backend (LeftOuterJoin a b) |
(Esqueleto query expr backend, FromPreprocess query expr backend (CrossJoin a b)) => From query expr backend (CrossJoin a b) |
(Esqueleto query expr backend, FromPreprocess query expr backend (InnerJoin a b)) => From query expr backend (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) |
(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) |
(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) |
(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) |
(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) |
(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) |

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

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

Instances

(Esqueleto query expr backend, PersistEntity val, ~ * (PersistEntityBackend val) backend) => FromPreprocess query expr backend (expr (Maybe (Entity val))) |
(Esqueleto query expr backend, PersistEntity val, ~ * (PersistEntityBackend val) backend) => FromPreprocess query expr backend (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) |