SQL efficient way to join a table where all values exist

Question

table 1
item    group_id
123     aaaa
432     bbbb
534     aaaa
765     cccc
656     aaaa
656     cccc
111     cccc

group_id    group_name
aaaa        groupA
bbbb           


        

Answer 1

SELECT DISTINCT t1.group_name 
                    FROM table1 t1 join table1 t2 join groups g
                        ON t1.group_id = t2.group_id 
                           and t1.item = 765 
                           and t2.item = 656
                           and g.group_id = t1.group_id