Ora-00905 missing keyword error

Question

Hi ,
Whats wrong with the below query?
Pls help
select state_id ,
       TO_CHAR(state_eff_date, 'dd-mon-yyyy hh24:mi:ss am'),
     case
          when station_id = null then state_id = lag(state_id) over (order by ash.station_id)
     end "previous_state"    
   from vppstation.avi_state_history
where state_eff_date >= to_date('01/02/2010', 'dd/mm/yyyy')
    and state_eff_date <= to_date('16/03/2010', 'dd/mm/yyyy')
    and station_id = 61 ;Thanks.

Answer 1

Consider this example:
  1* SELECT * FROM emp ORDER BY hiredate
SQL> /
     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
      7698 BLAKE      MANAGER           7839 01-MAY-81        2850              30
      7782 CLARK      MANAGER           7839 09-JUN-81        2450              10
      7844 TURNER     SALESMAN           7698 08-SEP-81        1500       0        30
      7654 MARTIN     SALESMAN           7698 28-SEP-81        1250       1400        30
      7839 KING       PRESIDENT         17-NOV-81        5000              10
      7900 JAMES      CLERK           7698 03-DEC-81         950              30
      7902 FORD       ANALYST           7566 03-DEC-81        3000              20
     EMPNO ENAME      JOB            MGR HIREDATE         SAL       COMM     DEPTNO
      7934 MILLER     CLERK           7782 23-JAN-82        1300              10
      7788 SCOTT      ANALYST           7566 19-APR-87        3000              20
      7876 ADAMS      CLERK           7788 23-MAY-87        1100              20
14 rows selected.
  1  WITH c_set AS
  2   (SELECT deptno, hiredate FROM emp WHERE hiredate BETWEEN DATE '1981-03-01' AND DATE '1981-03-30' AND deptno = 30)
  3  SELECT * FROM c_set
  4  UNION ALL
  5  SELECT deptno, MAX(hiredate)
  6   FROM  emp
  7   WHERE hiredate <= DATE '1981-03-30'
  8   AND   deptno = 30
  9   AND   0 = (SELECT COUNT(*) FROM c_set WHERE hiredate BETWEEN DATE '1981-03-01' AND DATE '1981-03-30' AND deptno = 30)
10*  GROUP BY deptno
SQL> /
    DEPTNO HIREDATE
     30 22-FEB-81
SQL> ed
Wrote file afiedt.buf
  1  WITH c_set AS
  2   (SELECT deptno, hiredate FROM emp WHERE hiredate BETWEEN DATE '1981-03-01' AND DATE '1981-05-30' AND deptno = 30)
  3  SELECT * FROM c_set
  4  UNION ALL
  5  SELECT deptno, MAX(hiredate)
  6   FROM  emp
  7   WHERE hiredate <= DATE '1981-05-30'
  8   AND   deptno = 30
  9   AND   0 = (SELECT COUNT(*) FROM c_set WHERE hiredate BETWEEN DATE '1981-03-01' AND DATE '1981-05-30' AND deptno = 30)
10*  GROUP BY deptno
SQL> /
    DEPTNO HIREDATE
     30 01-MAY-81