计算已被计数和分组的表的结果行

Question

我想计算计数结果并按表结果分组

像我有一个表， 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

我想计算此结果的总行数为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

...但是它给了我phpmyadmin这个错误

#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

这样做：

SELECT COUNT(DISTINCT name) FROM a

Answer 2

子选择将起作用，尽管可能更优雅。

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