| Safe Haskell | None |
|---|---|
| Language | Haskell2010 |
Opaleye.Distinct
- distinct :: Default Distinctspec fields fields => Select fields -> Select fields
- distinctExplicit :: Distinctspec columns columns' -> Query columns -> Query columns'
Documentation
distinct :: Default Distinctspec fields fields => Select fields -> Select fields Source #
Remove duplicate rows from the Select.
Example type specialization:
distinct :: Select (Column a, Column b) -> Select (Column a, Column b)
Assuming the makeAdaptorAndInstance splice has been run for the product type Foo:
distinct :: Select (Foo (Column a) (Column b) (Column c)) -> Select (Foo (Column a) (Column b) (Column c))
By design there is no distinct function of type SelectArr a b ->
SelectArr a b. Such a function would allow violation of SQL's
scoping rules and lead to invalid queries.
distinctExplicit :: Distinctspec columns columns' -> Query columns -> Query columns' Source #