写一个较为复杂的存储过程，包含游标

CREATE PROCEDURE complex_stored_procedure ()
BEGIN
DECLARE v_cursor CURSOR FOR
SELECT col1, col2, col3, col4
FROM table1;OPEN v_cursor;DECLARE CONTINUE HANDLER FOR NOT FOUND SET done = TRUE;SET done = FALSE;LOOP_LABEL: LOOP
FETCH v_cursor INTO var1, var2, var3, var4; IF done THEN
LEAVE LOOP_LABEL;
END IF; -- Do something with the variables hereEND LOOP LOOP_LABEL;CLOSE v_cursor;END;