Where clause help.

Question

Hi,
I have table with a partition on a column of date data type. Each partition has a month's data in it. I use the following query to fetch the data:
select column1, column2
from table1 partition(apr2011)
where trunc(date_column) = '01-APR-11';
The query works fast when partition has less records(data for 10-15 days). But as the number of records in the partition increases(at month end), the time taken to retrieve the result is much more. Request you to please help me with an alternative for the 'where clause' to get faster data.
Thanks.

Answer 1

Thanks Mohamed,
Finally the coin dropped
SQL> CREATE TABLE sales_range
(salesman_id  NUMBER(5),
sales_date    DATE)
PARTITION BY RANGE(sales_date)
PARTITION sales_jan2000 VALUES LESS THAN(TO_DATE('02/01/2000','MM/DD/YYYY')),
PARTITION sales_feb2000 VALUES LESS THAN(TO_DATE('03/01/2000','MM/DD/YYYY')),
PARTITION sales_mar2000 VALUES LESS THAN(TO_DATE('04/01/2000','MM/DD/YYYY')),
PARTITION sales_apr2000 VALUES LESS THAN(TO_DATE('05/01/2000','MM/DD/YYYY'))
Table created.
SQL> set autotrace traceonly explain
SQL> SELECT * FROM   sales_range
WHERE  sales_date = TO_DATE ( '03/01/2000', 'MM/DD/YYYY');
no rows selected.
Execution Plan
   0       SELECT STATEMENT Optimizer Mode=ALL_ROWS (Cost=2 Card=1 Bytes=97)
   1    0    PARTITION RANGE SINGLE (Cost=2 Card=1 Bytes=97)
   2    1      TABLE ACCESS FULL KORT.SALES_RANGE (Cost=2 Card=1 Bytes=97)
SQL> SELECT * FROM   sales_range
WHERE  TRUNC (sales_date) = TO_DATE ( '03/01/2000', 'MM/DD/YYYY');
no rows selected.
Execution Plan
   0       SELECT STATEMENT Optimizer Mode=ALL_ROWS (Cost=2 Card=1 Bytes=97)
   1    0    PARTITION RANGE ALL (Cost=2 Card=1 Bytes=97)
   2    1      TABLE ACCESS FULL KORT.SALES_RANGE (Cost=2 Card=1 Bytes=97)
Your explanation If using TRUNC, you don't get partition elimination
Regards
Peter