Analytic function question

Question

I have been trying to fix this since yesterday ad I am close, here is the question
CREATE TABLE P_X_STG
  PID  NUMBER,
  EID  VARCHAR2(10 BYTE)
CREATE TABLE TAB_C
  EID  VARCHAR2(10 BYTE),
  X    NUMBER
SET DEFINE OFF;
Insert into P_X_STG
   (PID, EID)
Values
   (1, 'e3');
Insert into P_X_STG
   (PID, EID)
Values
   (1, 'e1');
Insert into P_X_STG
   (PID, EID)
Values
   (1, 'e2');
Insert into P_X_STG
   (PID, EID)
Values
   (2, 'e3');
Insert into P_X_STG
   (PID, EID)
Values
   (2, 'e4');
Insert into P_X_STG
   (PID, EID)
Values
   (3, 'e5');
COMMIT;
SET DEFINE OFF;
Insert into TAB_C
   (EID, X)
Values
   ('e1', 100);
Insert into TAB_C
   (EID, X)
Values
   ('e3', 300);
Insert into TAB_C
   (X)
Values
   (400);
COMMIT;we match both the tables by eid
if the eid matches, get corresponding x information
if a pid has multiple different eids, for matching eid, get corresponding x information, but for non matching, simply put a NULL to x
for matching eids, print "ematch", for non matchig eids, print "pmatch"
in the below query, for non matching eids, we copy x information from matching ones, can someone help me substitute tha with Null
SELECT pid,
            eid,
            x,
            ematch
       FROM (  SELECT p.pid,
                      p.eid,
                      CASE
                         WHEN p.eid = c.eid THEN c.x
                         ELSE LAG (x) OVER (ORDER BY pid)
                      END
                         x,
                      CASE WHEN p.eid = c.eid THEN 'ematch' ELSE 'pmatch' END
                         ematch
                 FROM p_x_stg p, tab_c c
                WHERE p.eid = c.eid(+)
             ORDER BY pid, eid)
      WHERE x IS NOT NULL
   ORDER BY pid;
result is
1     e1     100     ematch
1     e2     100     pmatch
1     e3     300     ematch
2     e3     300     ematch
2     e4     300     pmatchI want below result
1    e1    100    ematch
1    e2    null    pmatch
1    e3    300    ematch
2    e3    300    ematch
2    e4    null    pmatchfor 1, e2 and 2, e4, instead of copying, just put null
Edited by: user650888 on Apr 6, 2012 12:29 PM

Answer 1

Hi,
user650888 wrote:
thanks, can this be combined into one query ?Do you mean without a sub-query?
Why? What's wrong with a sub-query?
If uisng a sub-query is the clearest and most efficient way to get the results you want, why wouldn't you want to use a sub-query?
Suppose there was a way, that involved some other technique. How would we know that you didn't object to that technique as well?
At any rate, I don't see how to do it without a sub-query. Analytic functions are computed after the WHERE clause is applied. If you want to use the results of an analytic function in a WHERE clause (as here, we want to use the results of the analytic COUNT function in a WHERE clause), then you have to compute the analytic function separately, in another (sub-) query.