Oracle SQL query performance - oracle

Question

I have 3 tables trader, city_state, city_present.
I have 4million rows in trader table and my query is taking atleast 20sec. Few records in city_present and cities table.
Below is my query.
select t.trader_id, t.name, t.city, t.state from
(
SELECT distinct c.city, c.state
FROM city_present p,city_state c
WHERE p.name = 'TEST_TEST'
AND c.city = p.city
AND c.state = p.state
)
cs, trader t
where
AND t.city = cs.city
AND t.state = cs.state
AND t.name = 'john test'
AND t.is_valid= 1
I have index on customer (city, state, name, valid_customer)
Subquery is taking less than a second .. it is outer query that is taking around 20sec.
Can someone please help me how to reduce the query time.

Answer 1

I assume you have an index on trader.name, possibly including trader.is_valid as well?
And is the distinct really required? Does that really need to be an in-line view, or could it be a regular join?

Answer 2

There are some things you can try without adding anything to your schema: in your subquery you never select anything from city_present, so you can turn it into IN / EXISTS
select t.trader_id, t.name, t.city, t.state from
(
SELECT c.city, c.state
FROM city_state c
WHERE EXISTS (
select null
from city_present p
where
p.name = 'TEST_TEST'
AND c.city = p.city
AND c.state = p.state)
)
cs, trader t
where
AND t.city = cs.city
AND t.state = cs.state
AND t.name = 'john test'
AND t.is_valid= 1
Then, the same thing applies to cs. So you could rewrite to:
select t.trader_id, t.name, t.city, t.state from
trader t
where
exists (
SELECT null
FROM city_state c
WHERE EXISTS (
select null
from city_present p
where
p.name = 'TEST_TEST'
AND c.city = p.city
AND c.state = p.state)
AND t.city = c.city
AND t.state = c.state
)
AND t.name = 'john test'
AND t.is_valid= 1
You can also try flattening the subqueries:
select t.trader_id, t.name, t.city, t.state from
trader t
where
exists (
SELECT null
FROM city_present p,city_state c
WHERE p.name = 'TEST_TEST'
AND c.city = p.city
AND c.state = p.state
AND t.city = c.city
AND t.state = c.state
)
AND t.name = 'john test'
AND t.is_valid= 1
From here, you should investigate about indexing:
trader.name and / or trader.id
(city_state.city, city_state.state) and (city_present.city, city_present.state)