CASE Statement error in function -- Please help!

Question

Hi All,
I created a function in my report.
It has a SQL query similar to the one below. The query works fine in SQL plus.
It has a CASE statement. I am getting error at line4 at the select statement. Error is: "Encountered symbol 'SELECT'....."
Can we use CASE statements like this in reports that use SELECT statements for RETURN EXPRESSIONS. Do we have to do any special?
Can someone help me out of this trouble?
THanks in advance.
SELECT PARENT_id,
     CASE WHEN EXISTS (SELECT PARENT_id FROM CHILD CH1 WHERE CH1.PARENT_id = PARENT.PARENT_id AND UPPER(CH1.description) LIKE '%ABC%') THEN
          (SELECT CH2.MOD_id FROM CHILD CH2 WHERE CH2.PARENT_id = PARENT.PARENT_id AND UPPER(CH2.description) LIKE '%ABC%')
     ELSE
          (SELECT MOD_id FROM
          (SELECT MOD_id,PARENT_id FROM CHILD CH3 ORDER BY started) MOD2 WHERE MOD2.PARENT_id = PARENT.PARENT_id AND ROWNUM = 1
     END
) MOD_ID
FROM PARENT;

Answer 1

take out the parentheses after the PARENT_ID and see
like below
SELECT parent_id,
       CASE
          WHEN EXISTS (
                 SELECT parent_id
                   FROM CHILD ch1
                  WHERE ch1.parent_id = PARENT.parent_id
                    AND UPPER (ch1.description) LIKE '%ABC%')
             THEN (SELECT ch2.mod_id
                     FROM CHILD ch2
                    WHERE ch2.parent_id = PARENT.parent_id
                      AND UPPER (ch2.description) LIKE '%ABC%')
          ELSE (SELECT mod_id
                  FROM (SELECT   mod_id, parent_id
                            FROM CHILD ch3
                        ORDER BY started) mod2
                 WHERE mod2.parent_id = PARENT.parent_id AND ROWNUM = 1)
       END AS mod_id
  FROM PARENT;