Decode in order by clause

Question

Is it possible to use a decode function in the order by clause, when you have two select statements with a union between? I seem to be getting an error-message telling me to type a number.
Can anybody help me?

Answer 1

Tove,
Is this what you mean?
SQL> SELECT
  2  *
  3  FROM
  4  (SELECT
  5      empno     no
  6  ,   ename     name
  7  ,   job       description
  8  FROM          emp
  9  UNION
10  SELECT
11      deptno    no
12  ,   dname     name
13  ,   loc       description
14  FROM          dept
15  )
16  ORDER BY
17  DECODE(1
18  ,      1,TO_CHAR(no)
19  ,      2,name
20  ,      3,description)
21  /
        NO NAME           DESCRIPTION
        10 ACCOUNTING     NEW YORK
        20 RESEARCH       DALLAS
        30 SALES          CHICAGO
        40 OPERATIONS     BOSTON
      7369 SMITH          CLERK
      7499 ALLEN          SALESMAN
      7521 WARD           SALESMAN
      7566 JONES          MANAGER
      7654 MARTIN         SALESMAN
      7698 BLAKE          MANAGER
      7782 CLARK          MANAGER
      7788 SCOTT          ANALYST
      7839 KING           PRESIDENT
      7844 TURNER         SALESMAN
      7876 ADAMS          CLERK
      7900 JAMES          CLERK
      7902 FORD           ANALYST
      7934 MILLER         CLERK
18 rows selected.Now, to order by the second column, I set the first parameter of the
DECODE to "2":
SQL> SELECT
  2  *
  3  FROM
  4  (SELECT
  5      empno     no
  6  ,   ename     name
  7  ,   job       description
  8  FROM          emp
  9  UNION
10  SELECT
11      deptno    no
12  ,   dname     name
13  ,   loc       description
14  FROM          dept
15  )
16  ORDER BY
17  DECODE(2
18  ,      1,TO_CHAR(no)
19  ,      2,name
20  ,      3,description)
21  /
        NO NAME           DESCRIPTION
        10 ACCOUNTING     NEW YORK
      7876 ADAMS          CLERK
      7499 ALLEN          SALESMAN
      7698 BLAKE          MANAGER
      7782 CLARK          MANAGER
      7902 FORD           ANALYST
      7900 JAMES          CLERK
      7566 JONES          MANAGER
      7839 KING           PRESIDENT
      7654 MARTIN         SALESMAN
      7934 MILLER         CLERK
        40 OPERATIONS     BOSTON
        20 RESEARCH       DALLAS
        30 SALES          CHICAGO
      7788 SCOTT          ANALYST
      7369 SMITH          CLERK
      7844 TURNER         SALESMAN
      7521 WARD           SALESMAN
18 rows selected.
SQL> SELECT
  2  *
  3  FROM
  4  (SELECT
  5      empno     no
  6  ,   ename     name
  7  ,   job       description
  8  FROM          emp
  9  UNION
10  SELECT
11      deptno    no
12  ,   dname     name
13  ,   loc       description
14  FROM          dept
15  )
16  ORDER BY
17  DECODE(3
18  ,      1,TO_CHAR(no)
19  ,      2,name
20  ,      3,description)
21  /
        NO NAME           DESCRIPTION
      7788 SCOTT          ANALYST
      7902 FORD           ANALYST
        40 OPERATIONS     BOSTON
        30 SALES          CHICAGO
      7369 SMITH          CLERK
      7934 MILLER         CLERK
      7900 JAMES          CLERK
      7876 ADAMS          CLERK
        20 RESEARCH       DALLAS
      7566 JONES          MANAGER
      7698 BLAKE          MANAGER
      7782 CLARK          MANAGER
        10 ACCOUNTING     NEW YORK
      7839 KING           PRESIDENT
      7499 ALLEN          SALESMAN
      7844 TURNER         SALESMAN
      7654 MARTIN         SALESMAN
      7521 WARD           SALESMAN
18 rows selected.I needed to put the TO_CHAR in the DECODE so all of the columns
by which I could potentially order are VARCHAR2's, else I was
getting
SQL> /
DECODE(1
ERROR at line 17:
ORA-01785: ORDER BY item must be the number of a SELECT-list expressionHTH
T.