How to Retrive Data using Case or any other method

Question

Hi All
i am new to Oracle, i have three tables. 1 )*Person* contains following data
id,     Name,      DOB
98,     sss,     01/01/2009
99,     rrr,     01/01/2009
100,     rws,     01/01/2009
2) Reference Table Contains Following Data
Person_ID,     Ref_type,     Reference
98,     AAA,     jk98923
98,     BBB,     io9898
99,     AAA,     nb6666
100,     BBB,     g10090
now i need all pesons who got reference AAA only, i dont want to use any where clause. this because i have to incoporate this logic in Business Objects Report.
i need output as follows
Person_ID,     Name,      Reference
98,     sss,     jk98923
99,     rrr,     nb6666
100,     rws,     NULL
guys i know this is so simple for you, please come back to me on this. many thanks in advance
Edited by: user11078264 on 17-Apr-2009 05:46

Answer 1

How about something like this (note the WITH clause was used to generate sample data)?
SQL > WITH person AS
  2  (
  3  SELECT 98  AS ID, 'sss' AS NAME, TO_DATE('01/01/2009','MM/DD/YYYY') AS DOB FROM DUAL UNION ALL
  4  SELECT 99  AS ID, 'rrr' AS NAME, TO_DATE('01/01/2009','MM/DD/YYYY') AS DOB FROM DUAL UNION ALL
  5  SELECT 100         AS ID, 'rws' AS NAME, TO_DATE('01/01/2009','MM/DD/YYYY') AS DOB FROM DUAL
  6  ),
  7  reference AS
  8  (
  9     SELECT 98       AS PERSON_ID, 'AAA' AS REF_TYPE, 'jk98923' AS REFERENCE FROM DUAL UNION ALL
10     SELECT 98       AS PERSON_ID, 'BBB' AS REF_TYPE, 'io9898' AS REFERENCE FROM DUAL UNION ALL
11     SELECT 99       AS PERSON_ID, 'AAA' AS REF_TYPE, 'nb6666' AS REFERENCE FROM DUAL UNION ALL
12     SELECT 100      AS PERSON_ID, 'BBB' AS REF_TYPE, 'g10090' AS REFERENCE FROM DUAL
13  )
14  SELECT     PERSON_ID
15  ,  NAME
16  ,  MAX(DECODE(REF_TYPE,'AAA',REFERENCE,NULL)) Reference
17  FROM       person
18  JOIN       reference ON person.id = reference.person_id
19  GROUP BY PERSON_ID, NAME
20  ORDER BY PERSON_ID
21  /
PERSON_ID NAM REFEREN
        98 sss jk98923
        99 rrr nb6666
       100 rws