Condition to return the value

Question

Hi,
The query below is written in case condition
SELECT
"POBJ_ID",
"Project Name",
"Object Name",
"CEMLI NAME",
CASE
WHEN rownum = 1 and "CP1" IS NOT NULL THEN "CP1"
WHEN rownum = 1 and "CP1" IS NULL THEN NULL
WHEN rownum > 1 and ( case when rownum = 1 and "CP1" IS NOT NULL THEN "CP1") is not null then
wwv_flow_item.SELECT_LIST(3,'Yes','Yes;Yes,No;No,NA;NA')
WHEN rownum > 1 and ( case when rownum = 1 and "CP1" IS NULL THEN "CP1") is not null then
null
END "CP1"
FROM
SELECT
NULL "POBJ_ID",
NULL "Project Name",
NULL "Object Name",
NULL "CEMLI NAME",
max(decode(rownum,1,CP.CHECK_POINTS,null)) "CP1",
max(decode(rownum,2,CP.CHECK_POINTS,null)) "CP2",
max(decode(rownum,3,CP.CHECK_POINTS,null)) "CP3",
max(decode(rownum,4,CP.CHECK_POINTS,null)) "CP4",
max(decode(rownum,5,CP.CHECK_POINTS,null)) "CP5",
max(decode(rownum,6,CP.CHECK_POINTS,null)) "CP6",
max(decode(rownum,7,CP.CHECK_POINTS,null)) "CP7",
max(decode(rownum,8,CP.CHECK_POINTS,null)) "CP8",
max(decode(rownum,9,CP.CHECK_POINTS,null)) "CP9",
max(decode(rownum,10,CP.CHECK_POINTS,null)) "CP10"
FROM CHECK_POINTS CP, PROJECTS PRO
WHERE PRO.ID = 7200 AND
PRO.ID = CP.PRO_ID AND
TAS_ID = 5588
GROUP BY PRO.PROJECT_NAME
UNION ALL
SELECT
pobj.id "POBJ_ID",
PRO.PROJECT_NAME "Project Name",
POBJ.NAME "Object Name",
PC.NAME "CEMLI NAME",
NULL "CP1",
NULL "CP2",
NULL "CP3",
NULL "CP4",
NULL "CP5",
NULL "CP6",
NULL "CP7",
NULL "CP8",
NULL "CP9",
NULL "CP10"
FROM PROJECTS PRO,PROJECT_OBJECTS POBJ,PROJECT_OBJECTS_CEMLI PC
WHERE
PRO.ID = 7200 AND
PRO.ID = POBJ.PRO_ID AND
PRO.ID = PC.PRO_ID AND
POBJ.ID = PC.POBJ_ID
The problem i am facing in case condition
CASE
WHEN rownum = 1 and "CP1" IS NOT NULL THEN "CP1"
WHEN rownum = 1 and "CP1" IS NULL THEN NULL
WHEN rownum > 1 and ( case when rownum = 1 and "CP1" IS NOT NULL THEN "CP1") is not null then
wwv_flow_item.SELECT_LIST(3,'Yes','Yes;Yes,No;No,NA;NA')
WHEN rownum > 1 and ( case when rownum = 1 and "CP1" IS NULL THEN "CP1") is not null then
null
END "CP1"
The 3rd condition is not working.
Please let me know that changes i need to make
Thanks
Sudhir

Answer 1

Hi, Sudhir
Sudhir_N wrote:
The problem i am facing in case condition
CASE
WHEN rownum = 1 and "CP1" IS NOT NULL THEN "CP1"
WHEN rownum = 1 and "CP1" IS NULL THEN NULL
WHEN rownum > 1 and ( case when rownum = 1 and "CP1" IS NOT NULL THEN "CP1") is not null then
wwv_flow_item.SELECT_LIST(3,'Yes','Yes;Yes,No;No,NA;NA')
WHEN rownum > 1 and ( case when rownum = 1 and "CP1" IS NULL THEN "CP1") is not null then
null
END "CP1"
The 3rd condition is not working. The 3rd WHEN condition:
WHEN rownum > 1  and ( case when rownum = 1 and "CP1" IS NOT NULL THEN "CP1") is not null  thenis never TRUE, because the 2 sub-conditions contradict each other.
If "rownum > 1" is TRUE, then "rownum = 1" is FALSE, the nested CASE returns NULL, and the 2nd sub-condition is FALSE.
If "rownum > 1" is FALSE, then it doesn't matter what the 2nd sub-condition is; the overall result will be FALSE.
Please let me know that changes i need to makeThat depends on what results you want.
Post a little sample data (CREATE TABLE and INSERT statments) and the resuts you want from that data, and someone sill help you do it.
Remember that ROWNUM is arbitrary unless the base "table" is actually a view or sub-query that has an ORDER BY clause. In your querry, the row where ROWNUM=1 may have ROWNUM=2 or ROWNUM=3 the next time you run the query, even though the data hasn't changed. That's not necessarily a mistake, but if that's what you want, then there may be several different results from your sample data that are all equally correct. In that event, give a couple of examples of acceptable and unacceptable results.
The WHEN clauses in a CASE expression are evaluated in order. When you get to the n-th WHEN, you know that none of the WHEN conditions 1, 2, 3, ..., n-1 are TRUE.
So instead of:
CASE
    WHEN rownum = 1 and "CP1" IS NOT NULL     THEN "CP1"
    WHEN rownum = 1 and "CP1" IS NULL          THEN NULL
END           AS "CP1"you could get the same results by saying:
CASE
    WHEN rownum = 1 and "CP1" IS NOT NULL     THEN "CP1"
    WHEN rownum = 1                    THEN NULL
END           AS "CP1"This may help in doing whatever it is you're trying to do.
NKU wrote:
Hi,
You cannot use ">" with rownum. It is a pseudo column and the values for this column are generated at run time. So using ">" is not possible.Actually, you can use > with ROWNUM.
The following example uses ROWNUM > 2 to label all but the first 2 rows as 'Later':
SELECT       ROWNUM
,       dname
,       CASE
          WHEN  ROWNUM > 2
          THEN  'Later'
          ELSE  'Earlier'
       END     AS case_expr
FROM       scott.dept
ORDER BY  dname
;Typical output:
`   ROWNUM DNAME          CASE_EXPR
         1 ACCOUNTING     Earlier
         4 OPERATIONS     Later
         2 RESEARCH       Earlier
         3 SALES          LaterApparantly, you're thinking of using "ROWNUM > x" as the sole condition in a WHERE clause. If x >= 1, then that will cause no rows to be selected.
Edited by: Frank Kulash on May 27, 2010 7:10 AM