避免完全扫描子查询

Question

I have a query which was working before I added the exist condition. After adding the exist condition , its going into loop forever and not getting back any results. I think the main reason for that is the full scan for every row level record. Can anyone please tell how to avoid that. The query below is an example of what I am trying to achieve.

Basically the condition is that a car can have many parts and if any one of the parts updated on changes for that car, we want to pick up all the parts. The part has detail table and I want to look at updates to the detail table.

select c.id, p.id
from car c join part p on p.car_id=c.id
where exists ( 
    select 1 
    from part p join pdetl pd on p.id=pd.part_id 
    where p.car_id=c.id and pd.updated_on > ?
)

Answer 1

EDITED: Modified the query to get all the parts associated to the car that had part(s) updated.

The inner query gets the parts that were updated. The outer query then pulls all the parts that are associated to the car:

select c.id, p.id
from car c join part p on p.car_id=c.id
where c.id in
(
  select c.id
  from car c join part p on p.car_id=c.id
  where exists ( 
                 select 1 
                 from pdetl pd 
                 where p.id=pd.part_id 
                   and pd.updated_on > ?
                )
)