Using nested queries with group by

You can use an asterisk in a nested group by query as long as the group-by table has a single column, such as:

1> select * from t1
2> where c1 in (select * from t2 group by c1)
3> go

The nested group by query example is equivalent to:

1> select * from t1
2> where c1 in (select c1 from t2 group by c1)
3> go