mysql - 请问如何统计group by 后的结果

问题描述

比如这条语句可以统计查询总数

SELECT COUNT(`id`) AS `num` FROM `test`;

那如果加了一句group by 之后就不对了

SELECT COUNT(`id`) AS `num` FROM `test` GROUP BY `id`;

请问我想要知道GROUP BY出来有多少行数据，怎么做

问题解答

统计GROUP BY后的数据行数：

SELECT count(1) FROM ( SELECT * FROM `test` GROUP BY `id`) AS tmp;

统计id相同出现的次数：

SELECT id, count(1) FROM `test` GROUP BY `id`;

统计GROUP BY后的数据总和：

SELECT sum(c) FROM ( SELECT count(1) AS c FROM `test` GROUP BY `id`) AS tmp;

不清楚你想要查什么，但猜测是第一条SQL。

SELECT id,COUNT(id) AS num FROM test GROUP BY id;

楼主正解，思路就是先把查找到的结果放在一张“临时表”，然后再统计总数

楼上正解，题主可参考