数据库|mysql教程
游标,开发,如何
数据库-mysql教程
MYSQL存储过程开发中如何使用游标嵌套 在实际业务逻辑开发中，难免用到游标嵌套，举例如下： 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_cntINT DEFAULT 0 ; DECLARE l_doneINT DEFAULT 0;DECLARE grade_csr cursor FOR SELECT grade_id FROM org_grade; DECLARE class_csr cursor FORSELECT class_id FROM org_class WHERE grade_id=l_grade_id; DECLARE CONTINUE HANDLER FOR NOT FOUND SET l_done=1; OPEN grade_csr; grade_loop: LOOP — Loop through org_grade FETCH grade_csr into l_grade_id;select concat(‘年级：’, 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(‘ 班级：’, l_class_id); END LOOP; CLOSE class_csr; SET l_done=0;END LOOP grade_loop; CLOSE grade_csr; END;// delimiter ; /////////////////////////////////////////////////////////另一个例子：CREATE PROCEDURE curdemo() NOT DETERMINISTIC CONTAINS SQL SQL SECURITY DEFINER COMMENT ” BEGIN declare done1,done2 int default 0; declare name1,name2 varchar(20); declare id1,id2 int; 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;until done2 end repeat; close cur2; set done2=0; end; end if; until done1 end repeat; close cur1; commit; END; /// 作者 蔡磊
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