Opaleye.Column

Documentation

null :: Column (Nullable a)

A NULL of any type

isNull :: Column (Nullable a) -> Column Bool

matchNullable :: Column b -> (Column a -> Column b) -> Column (Nullable a) -> Column b

The Opaleye equivalent of the maybe function

fromNullable :: Column a -> Column (Nullable a) -> Column a

The Opaleye equivalent of the fromMaybe function

toNullable :: Column a -> Column (Nullable a)

data Column a

The Num and Fractional instances for Column a are too general. For example, they allow you to add two Column Strings. This will be fixed in a subsequent release.

Instances

Default ViewColumnMaker String (Column a)

Default QueryRunnerColumn a b => Default QueryRunner (Column a) b

Default Binaryspec (Column a) (Column a)

Default Unpackspec (Column a) (Column a)

Default Valuesspec (Column Int) (Column Int)

Default NullMaker (Column a) (Column (Nullable a))

Default NullMaker (Column (Nullable a)) (Column (Nullable a))

Default ColumnMaker (Column a) (Column a)

Default Distinctspec (Column a) (Column a)

(ShowConstant a, Fractional a) => Fractional (Column a)

(ShowConstant a, Num a) => Num (Column a)

Show (Column a)

data Nullable a

Instances

Default NullMaker (Column a) (Column (Nullable a))

Default NullMaker (Column (Nullable a)) (Column (Nullable a))

Default QueryRunnerColumn a b => Default QueryRunnerColumn (Nullable a) (Maybe b)

unsafeCoerce :: Column a -> Column b