mysql - 统计已经统计并分组的表的结果行

Question

我想统计counted和group by table结果的结果

就像我有一张桌子，a：

id |name
1  |abc
2  |abc
3  |abc
4  |xyz
5  |xyz 

我的查询是SELECT COUNT(id) as count_id from a GROUP BY name

...给出结果：

count_id
3
2

我想计算这个结果的总行数，即 2

所以我的查询是SELECT COUNT(SELECT COUNT(id) as count_id from a GROUP BY name) as maincount from a

...但它给了我这个错误phpmyadmin

#1064 - You have an error in your SQL syntax; check the manual that corresponds to your MySQL server version for the right syntax to use near 'SELECT count.....

Answer 1

只需这样做：

SELECT COUNT(DISTINCT name) FROM a

Answer 2

尽管可能更优雅，但子选择会起作用。

  Select count(*) from (SELECT COUNT(id) as count_id from a GROUP BY name) as b