How to Use cursor nesting in MYSQL stored procedure development

In MYSQL stored procedure development, how to use cursors for nesting is inevitable in actual business logic development. For example: delimiter // drop PROCEDURE if exists good_nested_cursors1 // CREATE procedure good_nested_cursors1 () reads SQL DATABEGIN DECLARE l_grade_id INT; DECLARE l_class_id INT; DECLARE l_class_cnt INT DEFAULT 0; DECLARE l_done INT DEFAULT 0; www.2cto.com DECLARE grade_csr cursor FOR SELECT grade_id FROM org_grade; DECLARE class_csr cursor for select class_id FROM org_class WHERE grade_id = maid; declare continue handler for not found set l_done = 1; OPEN grade_csr; grade_loop: LOOP -- Loop through org_grade FETCH grade_csr into begin; select concat ('grade: ', l_grade_id); IF l_done = 1 then leave grade_loop; end if; OPEN class_csr; SET l_class_cnt = 0; class_loop: LOOP -- Loop through class in grade. FETCH class_csr INTO l_class_id; IF l_done = 1 then leave class_loop; end if; SET l_class_cnt = l_class_cnt + 1; select concat ('class: ', l_class_id); end loop; CLOSE class_csr; SET l_done = 0; www.2cto.com end loop grade_loop; CLOSE grade_csr; END; // delimiter; //////////////////////////////////////// /// // another example: create procedure curdemo () not deterministic contains SQL SECURITY DEFINER COMMENT ''BEGIN declare done1, done2 int default 0; declare name1, name2 varchar (20); declare id1, id2 int; www.2cto.com declare cur1 cursor for select id, name from test1; declare continue handler for not found set done1 = 1; open cur1; repeat fetch cur1 into id1, name1; if not done1 then insert into test3 (name) values (name1); begin declare cur2 cursor for select id, name from test2; declare continue handler for not found set done2 = 1; open cur2; repeat fetch cur2 into id2, name2; if not done2 then insert into test3 (name) values (name2); end if; www.2cto.com until done2 end repeat; close cur2; set done2 = 0; end if; until done1 end repeat; close cur1; commit; END; // by Cai lei