CREATE OR REPLACE FUNCTION add_missing_stocks() RETURNS void AS
$$
DECLARE
    proCursor CURSOR FOR SELECT pro_id FROM Product;
    proId Product.pro_id%TYPE;
    warCursor CURSOR FOR SELECT war_id FROM Warehouse;
    warId Warehouse.war_id%TYPE;
BEGIN
    RAISE NOTICE 'Start';

    -- Iterate on products
    OPEN proCursor;
    LOOP
        FETCH proCursor INTO proId;
        EXIT WHEN proId IS NULL;

        -- Iterate on warehouses
        OPEN warCursor;
        LOOP
            FETCH warCursor INTO warId;
            EXIT WHEN warId IS NULL;
            RAISE NOTICE 'Pro % for war %', proId, warId;
        END LOOP;
        CLOSE warCursor;
    END LOOP;
    CLOSE proCursor;
    RAISE NOTICE 'End';
END;
$$
LANGUAGE plpgsql;