SQL 按多列分组
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SQL Group by multiple columns
提问by Andrei Coman
I have the following table
我有下表
CREATE TABLE actions (id INTEGER PRIMARY KEY, key1 NUMERIC, key2 NUMERIC);
I'm not even sure how to explain this so I think it's best i give an example:
我什至不知道如何解释这一点，所以我认为最好举个例子：
id key1 key2
1 1 1
2 1 2
3 1 1
4 2 1
5 2 3
to ouput something like this:
输出这样的东西：
key1 key2 count(id)
1 1 2
1 2 1
2 1 1
2 3 1
I tried something like this, but it doesn't work, because i need the key1 field to not be unique :
我试过这样的事情，但它不起作用，因为我需要 key1 字段不是唯一的：
Select key1,key2,count(id) from actions group by key2, order by key1
Thanks a lot
非常感谢
回答by gcooney
SELECT key1, key2, COUNT(id) FROM actions GROUP BY key1, key2 ORDER BY key1, key2
回答by eKek0
In the GROUP clause, you have to write allthe fields that aren't in the agregate (COUNT, MAX, MIN). So, in this case, you need to add the key1 field, as this:
在 GROUP 子句中，您必须编写所有不在聚合中的字段（COUNT、MAX、MIN）。因此，在这种情况下，您需要添加 key1 字段，如下所示：
Select key1, key2, count(id)
from actions
group by key1, key2
order by key1
