Function "IN" usage...

Question

It may be a naive question, but is the below sql allowed in sql and plsql? (using two columns with IN function)
select e.*
from employees e
where (e.dept_name,e.dept_num) in (select d.dept_name,d.dept_num
from departments);
Thanks in advance for your replies.
Sayeed

Answer 1

please note that not in is not reverse in:
SQL>  select 1 from dual where (1) in (select 1 from dual union
  2                                    select 2 from dual union
  3                                    select 3 from dual union
  4                                    select null from dual);
         1
         1
SQL>   select 1 from dual where (1) not in (select 2 from dual union
  2                                         select 3 from dual union
  3                                         select null from dual);
no rows selectedthis is becouse -
in is 1 = 1 or 1 = 2 or 1 = 3 or 1 = null
vs
not in is 1 = 2 and 1 = 3 and 1 = null (comparing somthing to null will always give false, so the exp is false)
Amiel.