Select a null value

Question

Hi to all , if anybody knows how to tackle with the following situation, please reply urgently. Thanx in advance.
Suppose I have a table EMPLOYEE , with EMPLOYEE_ID as primary key , as:
E_ID EMPLOYEE_NAME
1                        abc
3                      pqr
6                      xyz
I want to fire a query as
" select E_ID from EMPLOYEE where E_ID IN ( 1, 8 , 6) "
The result is as
1
6
But I want a result as null ( or any other indication) for the record which is null , i.e I want a result as
1
null
6
I have tried nvl, but dont get result as per my excepttation. Any clue , how to do this ? How should I write my query so that I will have the desired result. In desired result instead of null , any value or indication is acceptable.

Answer 1

Here's how i understand your problem. You have a table with n records. You run a query with an IN argument list. Rows that match the argument list should be returned by the query as they are, but for arguments that have no corresponding row in the table a row should be returned indicating the status. I have come up with a solution, though a bit complicated one. To test it first run following script and then execute the query at the end.
CREATE TABLE employee
(E_ID number,
EMPLOYEE_NAME varchar2(30))
INSERT INTO employee
values(1,'A')
INSERT INTO employee
values(2,'B')
INSERT INTO employee
values(3,'C')
CREATE OR REPLACE TYPE emp_type AS OBJECT
(E_ID number,
EMPLOYEE_NAME varchar2(30));
CREATE OR REPLACE TYPE emp_tab_typ AS TABLE OF emp_type;
CREATE OR REPLACE TYPE arg_list_typ AS VARRAY(20)
OF NUMBER;
CREATE OR REPLACE FUNCTION emp_fun(p_arg arg_list_typ) RETURN emp_tab_typ
IS
  v_emp_tab emp_tab_typ:=new emp_tab_typ();
  v_cnt number:=0;
BEGIN
   FOR r IN 1..p_arg.count LOOP
           v_cnt:=0;
           FOR x IN (SELECT E_ID,EMPLOYEE_NAME
                   FROM employee
                   WHERE E_ID=p_arg(r)) LOOP
                   v_emp_tab.extend;
                   v_emp_tab(v_emp_tab.count):=emp_type(x.E_ID,x.EMPLOYEE_NAME);
                   v_cnt:=1;
           END LOOP;
           IF v_cnt=0 THEN
                   v_emp_tab.extend;
         v_emp_tab(v_emp_tab.count):=emp_type(null,null);
           END IF;
   END LOOP;
   RETURN v_emp_tab;
END;
SQL> SELECT E_ID,nvl(EMPLOYEE_NAME,'Not Found')
  2  FROM TABLE(CAST(emp_fun(arg_list_typ(1,3,4)) AS emp_tab_typ))
  3  /
      E_ID NVL(EMPLOYEE_NAME,'NOTFOUND')
         1 A
         3 C
           Not Found
3 rows selected.--------------
Anwar