stored procedure with parameters mysql
-- Stored Procedure with parameters with default
-- this examble return all clients in all states if parameter is NULL
DELIMITER $$
CREATE PROCEDURE get_clients_by_state
(
	state CHAR(2)
)
BEGIN
	SELECT 
		*
	FROM
		clients c
    WHERE c.state =  IFNULL(state, c.state);
END $$
DELIMITER ;
-- Once you save the stored procedure, you can invoke it by using the CALL statement:
CALL get_client_by_state(NULL);