SQL Group by multiple columns

Question

I have the following table

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:

id  key1 key2
1   1    1
2   1    2
3   1    1
4   2    1
5   2    3

to ouput something like this:

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 :

Select  key1,key2,count(id)  from actions group by key2, order by key1

Thanks a lot

Answer 1

SELECT key1, key2, COUNT(id) FROM actions GROUP BY key1, key2 ORDER BY key1, key2

Answer 2

In the GROUP clause, you have to write all the fields that aren't in the agregate (COUNT, MAX, MIN). So, in this case, you need to add the key1 field, as this:

Select  key1, key2, count(id)  
from actions 
group by key1, key2 
order by key1