Improve the performance of SELECT query

rahul_desai29 · New User Joined: 15 Mar 2006 Posts: 10 Location: fl;jds

SELECT * it is running very slow,how you will make it faster?

priyesh.agrawal · Posted: Tue Mar 21, 2006 12:58 pm

KS · New User Joined: 28 Feb 2006 Posts: 91 Location: Chennai

Hi,
It is not the correct standard to give a select a query with *.This statement will result in excessive I/O overhead.
1. Instead of '*' , give the column names on which u need to select
2. Give necessary where clause
3. If u r tring to fetch rows from a larger db , thenuse FETCH FIRST 100 ROWS ONLY;
ex-
SELECT TRANS_NO , ST_DATE FROM EMPLOYEE.TABLE1
WHERE TRANS_NO = 7458959
ORDER BY TRANS_NO DESC
FETCH FIRST 100 ROWS ONLY ;

Thanks,
Ks

Gautam512 · Posted: Wed Mar 22, 2006 3:47 pm

i totally accept what KuttiSatha said,

Select * always increases the I/O overhead.

Better to give the required column names.

One more important thing which increases the efficiency is,

for every column in a table there will be assigned indices (order of preference) if u use the same order for the column selected in the select query u'll surely increase the efficiency.

priyesh.agrawal · Posted: Wed Mar 22, 2006 4:15 pm

You may also want to code "FOR FETCH ONLY" to improve preformance, in case your query is read-only.

Regards,
Priyesh.