DB version: 11.2
Why can't I ORDER BY in this UNION ?
SQL> set lines 200 pages 200
SQL> select * from emp;
EMPNO ENAME JOB MGR HIREDATE SAL COMM DEPTNO
---------- ---------- --------- ---------- --------- ---------- ---------- ----------
7369 SMITH CLERK 7902 17-DEC-80 800 20
7499 ALLEN SALESMAN 7698 20-FEB-81 1600 300 30
7521 WARD SALESMAN 7698 22-FEB-81 1250 500 30
7566 JONES MANAGER 7839 02-APR-81 2975 20
7654 MARTIN SALESMAN 7698 28-SEP-81 1250 1400 30
7698 BLAKE MANAGER 7839 01-MAY-81 2850 30
7788 SCOTT ANALYST 7566 19-APR-87 3000 20
7839 KING PRESIDENT 17-NOV-81 5000 10
7844 TURNER SALESMAN 7698 08-SEP-81 1500 0 30
7876 ADAMS CLERK 7788 23-MAY-87 1100 20
7900 JAMES CLERK 7698 03-DEC-81 950 30
7902 FORD ANALYST 7566 03-DEC-81 3000 20
12 rows selected.
--- Creating a clone of emp for demo purpose
SQL> create table emp_clone as select * From emp;
Table created.
SQL> select * from emp
union
select * from emp_clone order by hiredate asc;
select * from emp_clone order by hiredate asc
*
ERROR at line 3:
ORA-00904: "HIREDATE": invalid identifier
-- Attempt2 (Same error )
select * from emp
union
select * from emp_clone ec order by ec.hiredate asc;
ERROR at line 3:
ORA-00904: "EC"."HIREDATE": invalid identifier