游标嵌套遍历

user表：

CREATE DEFINER=`root`@`localhost` PROCEDURE `test`()BEGIN DECLARE user1 VARCHAR(100); DECLARE user2 VARCHAR(100); DECLARE done INT DEFAULT 0; DECLARE cursor_user1 CURSOR FOR(SELECT `name` FROM `user`); -- 定于游标1 DECLARE cursor_user2 CURSOR FOR(SELECT `name` FROM `user`); -- 定义游标2 DECLARE CONTINUE HANDLER FOR NOT FOUND SET done = 1; -- 结束标识 OPEN cursor_user1; -- 开启游标1 loop_1: LOOP -- 外层循环 -- ------------------------------------------------------------------------------------- # 尝试从游标1指向的数据集合获取数据，如果集合已经遍历完毕，done的值被设置为1。 FETCH cursor_user1 INTO user1; IF done = 1 THEN LEAVE loop_1; END IF; -- 外层循环结束条件 OPEN cursor_user2; -- 开启游标2 loop_2: LOOP -- 内层循环 -- ----------------------------------------------------------------------------- # 尝试从游标2指向的数据集合获取数据，如果集合已经遍历完毕，done的值被设置为1。 FETCH cursor_user2 INTO user2; IF done = 1 THEN LEAVE loop_2; END IF; -- 内层循环结束条件 # do something... -- ----------------------------------------------------------------------------- END LOOP loop_2; CLOSE cursor_user2; -- 关闭游标2 SET done = 0; -- important -- ------------------------------------------------------------------------------------ END LOOP loop_1; CLOSE cursor_user1; -- 关闭游标1END

测试

user表数据：

CREATE DEFINER=`root`@`localhost` PROCEDURE `test`()BEGIN DECLARE result VARCHAR(2000) DEFAULT ‘result‘; DECLARE user1 VARCHAR(100); DECLARE user2 VARCHAR(100); DECLARE done INT DEFAULT 0; DECLARE cursor_user1 CURSOR FOR(SELECT `name` FROM `user`); -- 定于游标1 DECLARE cursor_user2 CURSOR FOR(SELECT `name` FROM `user`); -- 定义游标2 DECLARE CONTINUE HANDLER FOR NOT FOUND SET done = 1; -- 结束标识 OPEN cursor_user1; -- 开启游标1 loop_1: LOOP -- 外层循环 -- ------------------------------------------------------------------------------------- # 尝试从游标1指向的数据集合获取数据，如果集合已经遍历完毕，done的值被设置为1。 FETCH cursor_user1 INTO user1; IF done = 1 THEN LEAVE loop_1; END IF; -- 外层循环结束条件 OPEN cursor_user2; -- 开启游标2 loop_2: LOOP -- 内层循环 -- ----------------------------------------------------------------------------- # 尝试从游标2指向的数据集合获取数据，如果集合已经遍历完毕，done的值被设置为1。 FETCH cursor_user2 INTO user2; IF done = 1 THEN LEAVE loop_2; END IF; -- 内层循环结束条件 # do something... SET result = CONCAT(result,‘;‘,user1,‘-‘,user2); -- ----------------------------------------------------------------------------- END LOOP loop_2; CLOSE cursor_user2; -- 关闭游标2 SET done = 0; -- important -- ------------------------------------------------------------------------------------ END LOOP loop_1; CLOSE cursor_user1; -- 关闭游标1 SELECT result; END

执行结果：