SQL Help - Using Minus command

Question

Hey Sql forum
I'm using ver: Oracle 8.1.7.0.0
Quick Question for all of you.
I'm trying to run this query.
When I add my order by on each select statement the query doesn't work.
But when I remove the two order by statements on each query it works just fine.
Why is that?
Please get back to me thanks.
Query:
select
b.em_employee_id,
b.tcf_date_worked,
b.tcf_hours,
b.tcf_pdt_code,
b.tcf_payroll_unit
from tcf b
where b.tcf_year = '2006' and b.tcf_run_id in ('XXXX')
order by b.em_employee_id, b.tcf_date_worked, b.tcf_pdt_code, b.tcf_hours
minus
select
a.em_employee_id,
a.tcfa_date_worked,
a.tcfa_hours,
a.tcfa_pdt_code,
a.tcfa_payroll_unit
from tcfa a
where a.tcfa_year = '2006' and a.tcfa_run in ('1234')
order by a.em_employee_id, a.tcfa_date_worked, a.tcfa_pdt_code, a.tcfa_hours ;
}

Answer 1

Using the positional notation (1,2,3...) is often frowned upon because a change in the order of the columns in your select lists will cause the query to be sorted differently.
The other option is to use the appropriate column aliases so that the column names from both queries "line up". Then use the aliases in your order by.
SQL> select deptno dno, dname dnm
  2  from   dept
  3  union all
  4  select deptno dno, dname dnm
  5  from   dept
  6  order  by dnm, dno;
                 DNO DNM
                  10 ACCOUNTING
                  10 ACCOUNTING
                  40 OPERATIONS
                  40 OPERATIONS
                  20 RESEARCH
                  20 RESEARCH
                  30 SALES
                  30 SALES
8 rows selected.(used dept instead of dual)
Message was edited by:
Eric H