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1
END
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：
