Help needed on writing a SQL query

Question

Here is my table that shows records of 3 ORDER_ID (10, 20 and 30). All I need to do is, pick the first record of each order_id and check the event_id, if the event_id is same for the next record, ignore it, else show it and ignore rest all records for that order_id. This way my query output will show only two records for each ORDER_ID. Query should produce records that are in BOLD in the sample data. (Database - 11g)
Thanks for your help in advance
ORDER_ID     EVENT_ID     EVNT_DATE     STATE_CODE
*10     16937555     20100212     COMPLETE*
10     16937555     20100212     ACTIVE
*10     16308004     20100129     OCCURRED*
10     16131904     20100125     ACTIVE
10     16270684     20100128     OCCURRED
10     14899116     20091213     ACTIVE
10     16085672     20100123     COMPLETE
10     16085673     20100123     OCCURRED
10     14899119     20100123     COMPLETE
10     14899120     20100123     COMPLETE
*20     17134164     20100223     COMPLETE*
20     17134164     20100223     ACTIVE
20     17134164     20100223     STARTED
*20     15479131     20100105     OCCURRED*
20     15478409     20100105     OCCURRED
20     15478408     20100105     ACTIVE
20     15119404     20100105     COMPLETE
20     14346123     20091129     ACTIVE
20     15467821     20100104     OCCURRED
20     14346125     20091216     COMPLETE
20     14346126     20091215     COMPLETE
20     14346126     20091214     COMPLETE
*30     18814670     20100412     COMPLETE*
30     18814670     20100412     ACTIVE
*30     18029509     20100320     OCCURRED*
30     16853720     20100211     ACTIVE
30     17965764     20100319     OCCURRED
30     16386708     20100211     COMPLETE
30     16804451     20100211     OCCURRED
30     15977897     20100121     ACTIVE
Edited by: sarvan on Aug 12, 2011 7:16 AM

Answer 1

try this [Not fully tested]
SQL> select * from v$version;
BANNER
Oracle Database 11g Enterprise Edition Release 11.2.0.2.0 - 64bit Production
PL/SQL Release 11.2.0.2.0 - Production
CORE    11.2.0.2.0      Production
TNS for Linux: Version 11.2.0.2.0 - Production
NLSRTL Version 11.2.0.2.0 - Production
Elapsed: 00:00:00.00
SQL> SELECT *
  2    FROM (SELECT order_id, event_id, evnt_date, state_code, next_evntid,
  3                 ROW_NUMBER () OVER (PARTITION BY event_id ORDER BY NULL)
  4                                                                       AS rownm
  5            FROM (WITH t AS
  6                       (SELECT 10 AS order_id, 16937555 AS event_id,
  7                               20100212 AS evnt_date, 'COMPLETE' AS state_code
  8                          FROM DUAL
  9                        UNION ALL
10                        SELECT 10, 16937555, 20100212, 'ACTIVE'
11                          FROM DUAL
12                        UNION ALL
13                        SELECT 10, 16308004, 20100129, 'OCCURRED'
14                          FROM DUAL
15                        UNION ALL
16                        SELECT 10, 16131904, 20100125, 'ACTIVE'
17                          FROM DUAL
18                        UNION ALL
19                        SELECT 10, 16270684, 20100128, 'OCCURRED'
20                          FROM DUAL
21                        UNION ALL
22                        SELECT 20, 17134164, 20100223, 'COMPLETE'
23                          FROM DUAL
24                        UNION ALL
25                        SELECT 20, 17134164, 20100223, 'ACTIVE'
26                          FROM DUAL
27                        UNION ALL
28                        SELECT 20, 17134164, 20100223, 'STARTED'
29                          FROM DUAL
30                        UNION ALL
31                        SELECT 20, 15479131, 20100105, 'OCCURRED'
32                          FROM DUAL)  -- End of test data
33                  SELECT order_id, event_id, evnt_date, state_code,
34                         LEAD (event_id, 1, 0) OVER (PARTITION BY order_id ORDER BY NULL)
35                                                                 AS next_evntid
36                    FROM t)
37           WHERE event_id = next_evntid)
38   WHERE rownm <= 2
39  /
  ORDER_ID   EVENT_ID  EVNT_DATE STATE_CO NEXT_EVNTID      ROWNM
        10   16937555   20100212 COMPLETE    16937555          1
        20   17134164   20100223 COMPLETE    17134164          1
        20   17134164   20100223 ACTIVE      17134164          2
Elapsed: 00:00:00.00
SQL> PS - You should seriously think about ordering the data before you do this kind off operations.
Edited by: Sri on Aug 12, 2011 9:12 AM