{- Associate data in a many-to-many relation -}
(<~>) :: (IConnection c) => c -> (PairOfTypes, PairOfKeys) -> IO ()
conn <~> (ts, ks) = void(run conn query (SqlNull:sqlizePair ks))
    where query = uncurry getAssociate ts
(<~>) :: (IConnection c) => c -> (PairOfTypes, PairOfKeys) -> IO ()
conn <~> (ts, ks) = void(run conn query (SqlNull:sqlizePair ks))
    where query = uncurry getAssociate ts
conn <~> (ts, ks) = void(run conn query (SqlNull:sqlizePair ks))
    where query = uncurry getAssociate ts