Question

I have a load of items in a table. Each has a user_id.

I would like to find out the number of items per user as well as the total number of items.

If I do this:

SELECT COUNT(id)
FROM items
GROUP BY user_id

…I get the number of items per user but I can’t get the total number of items as they are grouped.

Is it possible to do this?

If so, is it a good way of doing things?

Would I be better of summing the counts after selecting them?

Answer 1

The following query will give you an additional row with the total number of items s and user_id=NULL.

SELECT user_id, COUNT(id) n_items
FROM items
GROUP BY user_id WITH ROLLUP

See also the Mysql docs on GROUP BY modifiers.