COUNT(*) problem with GROUP BY

[matsko]

What I'm trying todo is count the total amount of rows that match a series of tags that are related to one or more user_ids.

I've noticed that the COUNT(*) operation returns the total amount of rows that were calculated for each group by label.

so:

lets say that a user_id of 2 belongs to users_tags both in a record where the tag_id is 1 and 2.

SELECT user_id FROM users_tags WHERE tag_id IN (1,2)

I'm therefore going to end up getting two results.

SELECT user_id FROM users_tags WHERE tag_id IN (1,2) GROUP BY user_id.

Ok now I have 1 record (that's what I want), but when I run the count operation I get:

SELECT count(*) FROM users_tags WHERE tag_id IN (1,2) LIMIT 1

which gives me a value of two.

Now lets say that user_id of 3 also belongs to both tags.

then I'll get a count(*) of 4, but when I select columns I get two rows (which is the total count that I want).

How do I count the total amount of rows (using COUNT(*)) with a group by operation for this situation?

[r937]

depends on whether you're counting users or counting tags

what do you want to count?

[matsko]

I'm counting users.

I noticed that when I group by tag_id I get the count value that I want.