Help needed in debugging dynamic SQL.

Question

When I pass the p_deptno =30 and run the below code the refcursor returns the rows.But when I pass the dpetno =null then it goes to the condition if p_job is not null and throws an error.Can any one please help me in debugging this code.
declare
p_deptno number:=null;
p_job varchar2(30):='SALESMAN';
v_sql varchar2(4000);
l_ename varchar2(30);
  TYPE my_cursor IS REF CURSOR;
  RC my_cursor;
begin
  v_sql := 'select ename
            from emp
           where 1=1';
  if p_deptno is not null then
    v_sql := v_sql||' AND deptno='||p_deptno;
  else
    if p_job is not null then
      v_sql := v_sql||' AND job='||p_job;
    end if;
  end if;
  OPEN RC FOR v_sql;
  LOOP
    FETCH RC INTO l_ename;
    EXIT WHEN RC%NOTFOUND;
    dbms_output.put_line(l_ename);
  END LOOP;
  CLOSE RC;
END;Thanks.
Edited by: user3565577 on Mar 6, 2010 8:44 PM

Answer 1

Hi
I've mocked up a simple test and it seems to use the indexes when I try with one or the other values being supplied, I've made an assumption on the indexes you have (i.e. single column indexes on job and deptno),
--indexes on emp table:
p2056@dbapw01> @indexes
Enter value for table_name: emp
Enter value for owner: p2056
INDEX_OWNER                    INDEX_NAME                INDEX_TYPE                  PAR COLUMN_NAME                    STATUS
P2056                          EMPI1                     NORMAL                      NO  DEPTNO                         VALID
P2056                          EMPI2                     NORMAL                      NO  JOB                            VALID
2 rows selected.
--when accessing with a job value
p2056@dbapw01> explain plan for select *
  2  from emp
  3  where (
  4   (null is null and job = 'SALESMAN')
  5   OR
  6   ('SALESMAN' is null and deptno = null)
  7   OR
  8   ('SALESMAN' is null and null is null)
  9         );
Explained.
p2056@dbapw01> @xplan
PLAN_TABLE_OUTPUT
Plan hash value: 1888885832
| Id  | Operation                   | Name  | Rows  | Bytes | Cost (%CPU)| Time     |
|   0 | SELECT STATEMENT            |       |     2 |   154 |     1   (0)| 00:00:01 |
|   1 |  TABLE ACCESS BY INDEX ROWID| EMP   |     2 |   154 |     1   (0)| 00:00:01 |
|*  2 |   INDEX RANGE SCAN          | EMPI2 |     2 |       |     1   (0)| 00:00:01 |
Predicate Information (identified by operation id):
   2 - access("JOB"='SALESMAN')
--when accessing with a deptno value
p2056@dbapw01> explain plan for select *
  2  from emp
  3  where (
  4   (2 is null and job = null)
  5   OR
  6   (null is null and deptno = 2)
  7   OR
  8   (null is null and 2 is null)
  9         );
Explained.
p2056@dbapw01> @xplan
PLAN_TABLE_OUTPUT
Plan hash value: 1336173234
| Id  | Operation                   | Name  | Rows  | Bytes | Cost (%CPU)| Time     |
|   0 | SELECT STATEMENT            |       |     1 |    77 |     1   (0)| 00:00:01 |
|   1 |  TABLE ACCESS BY INDEX ROWID| EMP   |     1 |    77 |     1   (0)| 00:00:01 |
|*  2 |   INDEX RANGE SCAN          | EMPI1 |     1 |       |     1   (0)| 00:00:01 |
Predicate Information (identified by operation id):
   2 - access("DEPTNO"=2)