Database.Esqueleto

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.

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 BlogPosts), 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 ons 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 JOINs without ON clauses (either because you didn't do any JOIN, or because all JOINs already have their own ON clauses), a runtime exception OnClauseWithoutMatchingJoinException is thrown. ON clauses are optional when doing JOINs.

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 ons are applied on the reverse order that the JOINs 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 Maybes 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 newtypes, 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 Persons 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 UPDATEs. 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 JOINs.
• 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 JOINs.

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 JOINs.
• 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