Question

I have a table users:

user_id    name
1          John
2          Dan
3          Jane
4          Sophie
5          Jodie

I then have a table named associates:

user_id    assoc_id
1          2
1          3 
3          4
3          1
3          5
4          1
5          1
5          2

What I want to do is show how many associates each user has, or none

So, the results would show

user_id    Name     Number of Associates
1          John     2
2          Dan      0
3          Jane     3
4          Sophie   1
5          Jodie    2

What I’m trying works but does not show those with 0

Here’s what I’m trying, how do I get the 0s?

SELECT u.user_id, u.name, count(a.user_id) as howmany from users u
join associates a on a.user_id = u.user_id
group by u.user_id order by u.user_id asc

Answer 1

You need a LEFT OUTER JOIN:

SELECT u.user_id, u.name, count(a.user_id) as howmany 
FROM users u LEFT OUTER JOIN associates a 
ON a.user_id = u.user_id
GROUP BY u.user_id 
ORDER BY u.user_id ASC

The LEFT OUTER JOIN will include every rows of the first table even is they aren’t present in the joined table.