問題描述

比如這條語句可以統計查詢總數

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

那如果加了一句group by 之后就不對了

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

請問我想要知道GROUP BY出來有多少行數據，怎么做

問題解答

統計GROUP BY后的數據行數：

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

統計id相同出現的次數：

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

統計GROUP BY后的數據總和：

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，但猜測是第一條SQL。

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

樓主正解，思路就是先把查找到的結果放在一張“臨時表”，然后再統計總數

樓上正解，題主可參考