Fetching un-matching data

Question

Hi,
From the below code snippet, I want to fetch the non-matching data from table "T1".
DROP TABLE T1;
DROP TABLE T2;
CREATE TABLE T1
F1 INTEGER,
F2 VARCHAR2(100 BYTE),
F3 CHAR(1)
CREATE TABLE T2
FLD1 INTEGER,
FLD2 VARCHAR2(100 BYTE)
begin
     insert into t1
     values(1, 'A1', 'F');
     insert into t1
     values(1, 'A2', 'F');
     insert into t1
     values(1, 'A3', 'T');
     insert into t1
     values(2, 'A1', 'T');
     insert into t1
     values(3, 'A1', 'F');
     insert into t2
     values(1, 'T1');
     insert into t2
     values(2, 'T2');
end;
select * from t1;
select * from t2;
Query A)
select t1.*, nvl(t2.fld1, -1), nvl(t2.fld2, 'EMPTY')
from t1, t2
where t1.f1 = t2.fld1 (+);
Query B)
select t1.*, t2.*
from t1, t2
where t1.f3 = 'T' and t1.f1 = t2.fld1;
Upto this, it is fine, now, I want to fetch the resuts of "Query A" using something like given below,
without applying outer join, this would look silly, unfortunately cannot avoid it.
I am just trying to fetch the unmatching data from T1, when F3 field is
when "F3 = 'T'" then matching data using "t1.f1 = t2.fld1" should be fetched, otherwise
no join condition be applied.
I just tried using the below SQL, it gives "ORA-00905: missing keyword" error, I understand it is not correct.
select t1.*, t2.*
from t1, t2
where case when t1.f3 = 'T' then t1.f1 = t2.fld1 else NULL end;
I cannot use scalar subqueries for this requirement, as it is quite expensive, please give me other alternatives
for this, that should be helpful to me, thank you.

Answer 1

I'm kind of confused about your requirements.
Do you want to return ALL rows from T1 and only the values from T2 where T1.F3 = 'T'?
Something like this maybe?
SELECT  T1.*
                CASE
                        WHEN T1.F3 = 'T'
                        THEN NVL(T2.FLD1,-1)
                END
        )       AS FLD1
                CASE
                        WHEN T1.F3 = 'T'
                        THEN NVL(T2.FLD2,'EMPTY')
                END
        )       AS FLD2
FROM    T1
,       T2
WHERE   T1.F1 = T2.FLD1(+)Sample Results:
SQL > /
F1 F2  F FLD1 FLD2
  1 A3  T    1 T1
  1 A2  F
  1 A1  F
  2 A1  T    2 T2
  3 A1  FCan you please post the expected output as well?
We all appreciate that you posted sample data and the DDL to go with it can you post the following too?
1. Oracle version (e.g. 10.2.0.4)
2. Sample data, and expected output in \ tags (see FAQ for more information).
Edited by: Centinul on Aug 14, 2009 6:46 AM
Added query...