Question

I have a table that assign elements to groups. Each element can exist in many groups and can be assigned few times to the same group

it looks like:

element | group
      1 | 1
      1 | 2 
      1 | 3
      2 | 1
      2 | 3
      3 | 2

I’m looking for a simple query that can return me elements that are assigned to group 1, but NOT to group 2.

According to the presented data above this will be element 2.

Answer 1

select distinct element 
from  your_table
where element not in (select element 
                      from your_table 
                      where `group` = 2)
and `group` = 1