Ran into a weird problem when reviewing the result of one normal view. Here come the details --
I got the following SQL statement which is quite a simple outer join query,
select
items_table.item_key,
items_table.crm_type,
items_links.child_code,
items_links.mother_code
from
(
SELECT
name AS item_key,
CASE
WHEN type='Mitigant' AND datamart_table='COLLATERAL' THEN 'C'
WHEN type='Mitigant' AND datamart_table='GUARANTEE' THEN 'G'
ELSE NULL
END AS crm_type
FROM lo_prod_template
WHERE type = 'Mitigant'
) items_table,
(select 'dummy' as child_code, 'dummy' as mother_code from lo_prod_template) items_links
where
items_table.item_key = items_links.child_code(+)
As there is no record in the table LO_PROD_TEMPALTE with name as "dummy", the query (left outer join) should yeild "NULL" in the column child_code and mother_code, right? However, I got the following results presentd to me,
ITEM_KEY C CHILD_CODE MOTHER_CODE ------------------------------ - ------------------------------ ----------------------- Real Estate C dummy dummy DustinTestEntitySearch G dummy dummy Collateral Constrain by Min2 C dummy dummy DonnieTest2 C dummy dummy DonnieTestGuarantee G dummy dummy Guarantee G dummy dummy Guarantee Constrain Test Min G dummy dummy DonnieCollTest C dummy dummy Search Test Min2 G dummy dummy Search Coll Min C dummy dummy 10 rows selected.
This doesn't make any sense! Why does Oracle give me such result? After some trial-and-error work, I managed to get the expected results when removing the "CASE WHEN" clause in the query,
SQL> select 2 items_table.item_key, 3 items_table.crm_type, 4 items_links.child_code, 5 items_links.mother_code 6 from 7 ( 8 SELECT 9 name AS item_key, 10 type AS crm_type 11 /*CASE 12 WHEN type='Mitigant' AND datamart_table='COLLATERAL' THEN 'C' 13 WHEN type='Mitigant' AND datamart_table='GUARANTEE' THEN 'G' 14 ELSE NULL 15 END AS crm_type*/ 16 FROM lo_prod_template 17 WHERE type = 'Mitigant' 18 ) items_table, 19 (select 'dummy' as child_code, 'dummy' as mother_code from lo_prod_template) items_links 20 where 21 items_table.item_key = items_links.child_code(+) 22 / ITEM_KEY CRM_TYPE CHILD_CODE MOTHER_CODE ------------------------------ ------------------------------ ------------------------------ -------------- Real Estate Mitigant DustinTestEntitySearch Mitigant Collateral Constrain by Min2 Mitigant DonnieTest2 Mitigant DonnieTestGuarantee Mitigant Guarantee Mitigant Guarantee Constrain Test Min Mitigant DonnieCollTest Mitigant Search Test Min2 Mitigant Search Coll Min Mitigant 10 rows selected. SQL>
God... how could this happen? By the way, this behavior occurs in Oracle 11.2.0.2.
SQL> select * from v$version where rownum=1; BANNER ------------------------------------------------------------------------------- Oracle Database 11g Enterprise Edition Release 11.2.0.2.0 - 64bit Production SQL>
I tried to reproduct this issue in Oracle 10.2.0.4, but this time CASE WHEN works well. See -
SQL> select * from v$version where rownum=1; BANNER ---------------------------------------------------------------- Oracle Database 10g Enterprise Edition Release 10.2.0.4.0 - Prod SQL> select 2 items_table.item_key, 3 items_table.crm_type, 4 items_links.child_code, 5 items_links.mother_code 6 from 7 ( 8 SELECT 9 name AS item_key, 10 -- type as crm_type 11 CASE 12 WHEN type='Mitigant' AND datamart_table='COLLATERAL' THEN 'C' 13 WHEN type='Mitigant' AND datamart_table='GUARANTEE' THEN 'G' 14 ELSE NULL 15 END AS crm_type 16 FROM lo_prod_template 17 WHERE type = 'Mitigant' 18 ) items_table, 19 (select 'dummy' as child_code, 'dummy' as mother_code from lo_prod_template) items_links 20 where 21 items_table.item_key = items_links.child_code(+); ITEM_KEY C CHILD_CODE MOTHER_CODE ------------------------------ - ------------------------------ ------------------------------ Real Estate C DustinTestEntitySearch G Collateral Constrain by Min2 C DonnieTest2 C DonnieTestGuarantee G Guarantee G Guarantee Constrain Test Min G DonnieCollTest C Search Test Min2 G Search Coll Min C 10 rows selected. SQL>
So, I suspect this could be one Oracle bug.
