Gettting error for invalid identifier : SELECT emp. email_01 as online_id,
            emp. email_02 as primary_id,
            dept. email_03 as secondary_id
from 
(select distinct
           emp. email_01 as online_id,
            emp. email_02 as primary_id,
            dept. email_03 as secondary_id
    from emp, dept
    where emp.id=dept.id)
