Hi Waleed, > Oracle does not substitute the value of C2 in the expression. this could be achieved with two nested views using an expression e.g. (c2 - 10) in the inner view and referencing this new column in query of the outer. But this is apparently not the desired solution. I'd see a possible solution of this problem in a combination of partitioned views and partitioned tables (Jonathan mentioned it in his book, if I recall it correctly). Something like this: create or replace view v3 as select c1,c2,c3 from test_p_v where c2 >= 210 and c2 <= 309 and c1 >= 200 union all select c1,c2,c3 from test_p_v where c2 between 110 and 209 and c1 between 100 and 209 union all select c1,c2,c3 from test_p_v where c2 < 110 and c1 <= 99 ; So each UNION ALL subquery access at most 2 partitions. Note that this is only simplified solution to demonstrate the principle. select * from v3 where c2 = 150; Explaining this simple query you get following execution plan (10.1.0.2.0): ------------------------------------------------------------------------------------------------------- | Id | Operation | Name | Rows | Bytes | Cost (%CPU)| Time | Pstart| Pstop | ------------------------------------------------------------------------------------------------------- | 0 | SELECT STATEMENT | | 483 | 14490 | 342 (21)| 00:00:01 | | | | 1 | VIEW | V3 | 483 | 14490 | 342 (21)| 00:00:01 | | | | 2 | UNION-ALL PARTITION | | | | | | | | |* 3 | FILTER | | | | | | | | | 4 | PARTITION RANGE SINGLE | | 1 | 27 | 7622 (6)| 00:00:07 | 3 | 3 | |* 5 | TABLE ACCESS FULL | TEST_P_V | 1 | 27 | 7622 (6)| 00:00:07 | 3 | 3 | | 6 | PARTITION RANGE ITERATOR| | 60 | 1740 | 18148 (21)| 00:00:17 | 2 | 3 | |* 7 | TABLE ACCESS FULL | TEST_P_V | 60 | 1740 | 18148 (21)| 00:00:17 | 2 | 3 | |* 8 | FILTER | | | | | | | | | 9 | PARTITION RANGE SINGLE | | 1 | 26 | 7193 (6)| 00:00:07 | 1 | 1 | |* 10 | TABLE ACCESS FULL | TEST_P_V | 1 | 26 | 7193 (6)| 00:00:07 | 1 | 1 | ------------------------------------------------------------------------------------------------------- Predicate Information (identified by operation id): --------------------------------------------------- 3 - filter(210<=150) 5 - filter("C2"=150 AND "C2">=210 AND "C2"<=309) 7 - filter("C2"=150 AND "C2">=110 AND "C2"<=209 AND "C1"<=209) 8 - filter(110>150) 10 - filter("C2"=150 AND "C2"<110 AND "C1"<=99) A good question is if the obviously false filter (e.g. 210<=150) does prohibit the underlying table access. Some simple tests shows that this is OK and at most one union branch is executed if a equi-predicate on c2 is defined. See below. You may wont to verify some more complex queries on this view, usage of bind variables etc. HTH Jaromir D.B. Nemec http://www.db-nemec.com ---- some test -- 1) c2 out of range - instance responce 1 select count(*) from v3 2* where c2 = 550 SQL> / Elapsed: 00:00:00.01 2) test partition pruning, only the 1st partition should be accessed -- > OK, consistent gets corresponds to blocks of the partition 1 select count(*) from v3 2* where c2 = 109 SQL> / Elapsed: 00:00:04.32 Statistics ---------------------------------------------------------- 8 recursive calls 0 db block gets 18778 consistent gets 18758 physical reads 0 redo size 392 bytes sent via SQL*Net to client 512 bytes received via SQL*Net from client 2 SQL*Net roundtrips to/from client 0 sorts (memory) 0 sorts (disk) 1 rows processed SQL> set autotrace off SQL> select partition_name, 2 blocks 3 from user_tab_partitions a 4 where 5 table_name = upper('test_p_v'); PARTITION_NAME BLOCKS ------------------------------ ---------- P1 18765 P2 19785 P3 19913 Elapsed: 00:00:03.34 ----- Original Message ----- From: "Khedr, Waleed" <Waleed.Khedr@xxxxxxx> To: "jaromir nemec" <jaromir@xxxxxxxxxxxx>; <oracle-l@xxxxxxxxxxxxx> Sent: Thursday, March 03, 2005 3:37 AM Subject: RE: Anyway to optimize the optimizer -- //www.freelists.org/webpage/oracle-l