Question

I use SQL-Server 2008 and have the following tables.

users

userid
1
2
3

objects

objectid | category
9        | A
8        | B
7        | A
6        | C

userobjects

userid | objectid
1      | 9
3      | 7
3      | 6

As you can see, userobjects is a link table. Unfortunately it is missing some entries. I could include them with a script but I wonder if there is a solution in sql.

For every userid and every objectid that belongs to category ‘A’ there should be an entry in userobjects. So what I wanted to have is this:

userid | objectid
1      | 9
1      | 7
2      | 9
2      | 7
3      | 9
3      | 7
3      | 6

Answer 1

I could include them with a script but I wonder if there is a solution
in sql.

This is a select query using UNION (here is SQL-DEMO);

select u.userId, o.objectId
from objects o cross join users u
where o.category = 'A'
union
select u.userId, o.objectId
from users u join userobjects uj on u.userid = uj.userId
     join objects o on uj.objectid = o.objectid
where o.category <> 'A'
order by u.userid,o.objectid desc

--RESULTS
userId  objectId
1       9
1       7
2       9
2       7
3       9
3       7
3       6