Safe Haskell | None |
---|---|
Language | Haskell98 |
- distinct :: Default Distinctspec columns columns => Query columns -> Query columns
- distinctExplicit :: Distinctspec columns columns' -> Query columns -> Query columns'
Documentation
distinct :: Default Distinctspec columns columns => Query columns -> Query columns Source
Remove duplicate items from the query result.
Example type specialization:
distinct :: Query (Column a, Column b) -> Query (Column a, Column b)
Assuming the makeAdaptorAndInstance
splice has been run for the product type Foo
:
distinct :: Query (Foo (Column a) (Column b) (Column c)) -> Query (Foo (Column a) (Column b) (Column c))
By design there is no distinct function of type QueryArr a b ->
QueryArr 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