How to make this query go faster

Question

Hi ,
I have the following query :
select a.* from
tbl1 a , tbl2 b
where a.id = b.id
substr(b.id , 3, 2) <> 'XX'
and b.date1 is not null
and b.date1 >= sysdate - 90 ;
tbl1 - 21 million rows
tbl2 - 2 millions
i specify this hints /*+ INDEX(idxa_1 , idxa_2) INDEX(ixdb_1)
where idxa_1 --> b.lotid
idxa_2 --> b.date1
idxb_1 --> a.lotid
IF i DO NOT include b.date1 is not null and b.date1 >= sysdate - 90 ,
from explain plan i could see it using a FAST FULL SCAN which really returns very fast
HOWEVER if i include b.date1 is not null and b.date1 >= sysdate - 90
, from explain plain it uses row index and then there's a range scan and its slow
how can i improve the performance of this query ?
pls advise
tks & rdgs

Answer 1

Don't create the temporary table.
Create a function based index on table two
substr(id , 3, 2)Make sure you have gathered statistics on the tables.
Remove the hint.
select a.* from
tbl1 a , tbl2 b
where a.id = b.id
and substr(b.id , 3, 2) <> 'XX'
and b.date1 >= sysdate - 90;If you still have performance problems, post the formatted explain plan from sqlplus.
Read the Performance Tuning Guide.
Unfortunately this is not urs advice.