Opaleye.Join

Documentation

leftJoin :: (Default Unpackspec columnsA columnsA, Default Unpackspec columnsB columnsB, Default NullMaker columnsB nullableColumnsB) => Query columnsA -> Query columnsB -> ((columnsA, columnsB) -> Column PGBool) -> Query (columnsA, nullableColumnsB)

leftJoin's use of the Default typeclass means that the compiler will have trouble inferring types. It is strongly recommended that you provide full type signatures when using leftJoin.

Example specialization:

leftJoin :: Query (Column a, Column b)
         -> Query (Column c, Column (Nullable d))
         -> (((Column a, Column b), (Column c, Column (Nullable d))) -> Column PGBool)
         -> Query ((Column a, Column b), (Column (Nullable c), Column (Nullable d)))

leftJoinExplicit :: Unpackspec columnsA columnsA -> Unpackspec columnsB columnsB -> NullMaker columnsB nullableColumnsB -> Query columnsA -> Query columnsB -> ((columnsA, columnsB) -> Column PGBool) -> Query (columnsA, nullableColumnsB)