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GHC 10.0.0.20260917 · lts/ghc-10.0.x · 8fef28d · 2026-11-02

Moduleopaleye-0.10.8.0Haskell2010

Opaleye.Column

Deprecated. Use Opaleye.Field instead. Will be removed in version 0.11.

Functions for working directly with Columns.

Please note that numeric Column types are instances of Num, so you can use *, /, +, - on them.

Contents

Column
Working with NULL
Unsafe operations
Entire module

Synopsis

family Column
data Nullable
value null
value isNull
value unsafeCast
value unsafeCoerceColumn
value unsafeCompositeField
value isNull
value joinNullable
value null

Packageopaleye-0.10.8.0
Exports10
LanguageHaskell2010
LicenceBSD-3-Clause
SourceColumn.hs

Column

familytype family Column a where

Do not use. Use Field instead. Will be removed in a later version.

Equations

Column (Nullable a) = FieldNullable a
Column a = Field a

Working with `NULL`

datadata Nullable a

Only used within a Column, to indicate that it can be NULL. For example, a Column (Nullable SqlText) can be NULL but a Column SqlText cannot.

valuenull :: Column (Nullable a)

A NULL of any type

valueisNull :: Column (Nullable a) -> Column PGBool

TRUE if the value of the column is NULL, FALSE otherwise.

Unsafe operations

valueunsafeCast :: String -> Field_ n a -> Field_ n b

Cast a column to any other type. Implements Postgres's :: or CAST( ... AS ... ) operations. This is safe for some conversions, such as uuid to text.

valueunsafeCoerceColumn :: Field_ n a -> Field_ n' b

Treat a Column as though it were of a different type. If such a treatment is not valid then Postgres may fail with an error at SQL run time.

valueunsafeCompositeField :: Field_ n a -> String -> Field_ n' b

Entire module

valueisNull :: Column (Nullable a) -> Column PGBool

TRUE if the value of the column is NULL, FALSE otherwise.

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

valuenull :: Column (Nullable a)

A NULL of any type