Hoogle Search

Within LTS Haskell 24.32 (ghc-9.10.3)

Note that Stackage only displays results for the latest LTS and Nightly snapshot. Learn more.

  1. (<-.) :: forall v typ . PersistField typ => EntityField v typ -> [typ] -> Filter v

    persistent-mtl Database.Persist.Sql.Shim

    Check if value is in given list.

    Examples

    selectUsers :: MonadIO m => ReaderT SqlBackend m [Entity User]
selectUsers = selectList [UserAge <-. [40, 41]] []
    The above query when applied on dataset-1, will produce this: 
    +-----+-----+-----+
|id   |name |age  |
+-----+-----+-----+
|1    |SPJ  |40   |
+-----+-----+-----+
|2    |Simon|41   |
+-----+-----+-----+

    selectSPJ :: MonadIO m => ReaderT SqlBackend m [Entity User]
selectSPJ = selectList [UserAge <-. [40]] []
    The above query when applied on dataset-1, will produce this: 
    +-----+-----+-----+
|id   |name |age  |
+-----+-----+-----+
|1    |SPJ  |40   |
+-----+-----+-----+

  2. (<.) :: forall v typ . PersistField typ => EntityField v typ -> typ -> Filter v

    persistent-mtl Database.Persist.Sql.Shim

    Less-than check.

    Examples

    selectLessAge :: MonadIO m => ReaderT SqlBackend m [Entity User]
selectLessAge = selectList [UserAge <. 41 ] []
    The above query when applied on dataset-1, will produce this: 
    +-----+-----+-----+
|id   |name |age  |
+-----+-----+-----+
|1    |SPJ  |40   |
+-----+-----+-----+

  3. (<=.) :: forall v typ . PersistField typ => EntityField v typ -> typ -> Filter v

    persistent-mtl Database.Persist.Sql.Shim

    Less-than or equal check.

    Examples

    selectLessEqualAge :: MonadIO m => ReaderT SqlBackend m [Entity User]
selectLessEqualAge = selectList [UserAge <=. 40 ] []
    The above query when applied on dataset-1, will produce this: 
    +-----+-----+-----+
|id   |name |age  |
+-----+-----+-----+
|1    |SPJ  |40   |
+-----+-----+-----+

  4. (=.) :: forall v typ . PersistField typ => EntityField v typ -> typ -> Update v

    persistent-mtl Database.Persist.Sql.Shim

    Assign a field a value.

    Examples

    updateAge :: MonadIO m => ReaderT SqlBackend m ()
updateAge = updateWhere [UserName ==. "SPJ" ] [UserAge =. 45]
    Similar to updateWhere which is shown in the above example you can use other functions present in the module Database.Persist.Class. Note that the first parameter of updateWhere is [Filter val] and second parameter is [Update val]. By comparing this with the type of ==. and =., you can see that they match up in the above usage. The above query when applied on dataset-1, will produce this: 
    +-----+-----+--------+
|id   |name |age     |
+-----+-----+--------+
|1    |SPJ  |40 -> 45|
+-----+-----+--------+
|2    |Simon|41      |
+-----+-----+--------+

  5. (==.) :: forall v typ . PersistField typ => EntityField v typ -> typ -> Filter v

    persistent-mtl Database.Persist.Sql.Shim

    Check for equality.

    Examples

    selectSPJ :: MonadIO m => ReaderT SqlBackend m [Entity User]
selectSPJ = selectList [UserName ==. "SPJ" ] []
    The above query when applied on dataset-1, will produce this: 
    +-----+-----+-----+
|id   |name |age  |
+-----+-----+-----+
|1    |SPJ  |40   |
+-----+-----+-----+

  6. (>.) :: forall v typ . PersistField typ => EntityField v typ -> typ -> Filter v

    persistent-mtl Database.Persist.Sql.Shim

    Greater-than check.

    Examples

    selectGreaterAge :: MonadIO m => ReaderT SqlBackend m [Entity User]
selectGreaterAge = selectList [UserAge >. 40 ] []
    The above query when applied on dataset-1, will produce this: 
    +-----+-----+-----+
|id   |name |age  |
+-----+-----+-----+
|2    |Simon|41   |
+-----+-----+-----+

  7. (>=.) :: forall v typ . PersistField typ => EntityField v typ -> typ -> Filter v

    persistent-mtl Database.Persist.Sql.Shim

    Greater-than or equal check.

    Examples

    selectGreaterEqualAge :: MonadIO m => ReaderT SqlBackend m [Entity User]
selectGreaterEqualAge = selectList [UserAge >=. 41 ] []
    The above query when applied on dataset-1, will produce this: 
    +-----+-----+-----+
|id   |name |age  |
+-----+-----+-----+
|2    |Simon|41   |
+-----+-----+-----+

  8. (||.) :: [Filter v] -> [Filter v] -> [Filter v]

    persistent-mtl Database.Persist.Sql.Shim

    The OR of two lists of filters. For example: 

    selectList
([ PersonAge >. 25
, PersonAge <. 30 ] ||.
[ PersonIncome >. 15000
, PersonIncome <. 25000 ])
[]
    will filter records where a person's age is between 25 and 30 or a person's income is between (15000 and 25000). If you are looking for an (&&.) operator to do (A AND B AND (C OR D)) you can use the (++) operator instead as there is no (&&.). For example: 
    selectList
([ PersonAge >. 25
, PersonAge <. 30 ] ++
([PersonCategory ==. 1] ||.
[PersonCategory ==. 5]))
[]
    will filter records where a person's age is between 25 and 30 and (person's category is either 1 or 5).

  9. (!=.) :: forall v typ . PersistField typ => EntityField v typ -> typ -> Filter v

    persistent-redis Database.Persist.Redis

    Non-equality check.

    Examples

    selectSimon :: MonadIO m => ReaderT SqlBackend m [Entity User]
selectSimon = selectList [UserName !=. "SPJ" ] []
    The above query when applied on dataset-1, will produce this: 
    +-----+-----+-----+
|id   |name |age  |
+-----+-----+-----+
|2    |Simon|41   |
+-----+-----+-----+

  10. (*=.) :: forall v typ . PersistField typ => EntityField v typ -> typ -> Update v

    persistent-redis Database.Persist.Redis

    Assign a field by multiplication (*=).

    Examples

    multiplyAge :: MonadIO m => ReaderT SqlBackend m ()
multiplyAge = updateWhere [UserName ==. "SPJ" ] [UserAge *=. 2]
    The above query when applied on dataset-1, will produce this: 
    +-----+-----+--------+
|id   |name |age     |
+-----+-----+--------+
|1    |SPJ  |40 -> 80|
+-----+-----+--------+
|2    |Simon|41      |
+-----+-----+--------+

Page 150 of many | Previous | Next