Case help

Question

I'm using 9.2.0.5.0
I have a case in a where clause. The select is:
SELECT description,dist
FROM posdist
WHERE posname LIKE 'NAPOS'
AND to_char(nvl(active,9)) in CASE 2
WHEN 1
THEN '1'
WHEN 3
THEN '9'
WHEN 2
THEN (1,9)
END;
The column "active" is numeric. This query is going to end up being used as a dynamic statement in HTML DB. The case condition is going to be a field on the screen that the user will make a selection. The actual return value possibilities are 1 and NULL.
A value of 1 is active
A value of NULL is inactive
I am casting the column as a character because I was getting non-numeric errors from the last condition (WHEN 2) and the screen will return the values as character. I'm using the NVL function just to make the NULL's a 9 just so that they're easier to work with and compare.
The user may want both Active and Inactive records. This is my problem. I made the return value from the screen for INACTIVE a 3 to make the CASE easier to work with instead of trying to work with "nulls". As it stands now, the values of 1 and 3 works. The statement fails on the last condition - when the value is 2.
What I would like the where clause to be, of course, is when the value is 2 then the case resolve the last condition as: AND to_char(nvl(active,9)) in (1,9);
Again, when the values are 1 or 3 I get the correct records back.
Can someone help me out?
Thanks,
Joe

Answer 1

The only options for using IN are to have a static list or a query as your right hand operand. Obviously a static list won't accomplish what you want, but a query will. You allow 1 if the value you're considering is 1 or 3, and you allow 9 if the value you're considering is 1 or 2.
SELECT 1 FROM dual WHERE :x IN (1, 3)
UNION ALL
SELECT 9 FROM dual WHERE :x IN (1, 2)So then you can re-write your query as,
create table posdist (
posname  varchar2(30),
active  number,
dist  varchar2(30),
description  varchar2(80));
insert into posdist values ('NAPOS', 1, 'A', 'The letter A');
insert into posdist values ('NAPOS', 2, 'B', 'The letter B');
insert into posdist values ('NAPOS', 3, 'C', 'The letter C');
insert into posdist values ('NAPOS', 4, 'D', 'The letter D');
insert into posdist values ('NAPOS', 5, 'E', 'The letter E');
insert into posdist values ('NAPOS', 6, 'F', 'The letter F');
insert into posdist values ('NAPOS', 7, 'G', 'The letter G');
insert into posdist values ('NAPOS', 8, 'H', 'The letter H');
insert into posdist values ('NAPOS', 9, 'I', 'The letter I');
insert into posdist values ('NAPOS', 10, 'J', 'The letter J');
SELECT rownum
  FROM dual
COMMIT;
SQL> VAR x VARCHAR2
SQL>
SQL> exec :x := 2;
PL/SQL procedure successfully completed.
SQL>
SQL> SELECT description,
  2         dist
  3    FROM posdist
  4   WHERE posname LIKE 'NAPOS'
  5     AND TO_CHAR (NVL (active, 9)) IN (
  6           SELECT '1' FROM DUAL WHERE :x IN (1, 3)
  7           UNION ALL
  8           SELECT '9' FROM DUAL WHERE :x IN (1, 2)
  9         );
DESCRIPTION
DIST
The letter I
Inull