Question

I have a stored procedure, which returns a cursor.

The application passes a parameter to the procedure which determines how many ID`s should be fetched, so the procedure doesnt know a head of time that number.

foreach ID i need to fetch the top 3 records with that ID.
what I have tried is using:

select * from table_name where id in (List of ID`s);

That query works, but i cant get the top 3 of each ID. If i limit the result count, i will get the TOP results of the first ID.

I thought using For Loop, executing the query for each ID and append the results to the cursor, but as I understand it`s impossible.

Any Ideas ?

More details
Lets say I have 5 IDs and each of them have inner Ids so
Id 1 has (1,2,3,4,5) Id 2 (1,2,3,4,5) Id 3 (12,14,15,16,22) Id 4 (2,3,5,7,9) Id 5 (4,7,8,9,10)
In this case, which is the case I am dealing with, I dont see how row number will help me.
I need the top 3 for each ID, in this case the cursor should have 15 results.

10x alot and have a good weekend 😉

Answer 1

Presumably you have some criterion for determining the top three?

Anyway, the way to achieve this end is with an analytic function. Oracle offers three distinct functions: ROW_NUMBER(), RANK() and DENSE_RANK(). These offer three slightly different interpretations of TOP 3. Find out more.

Here is the basic idea, using ROW_NUMBER(), which will return exactly three rows for each ID.

open rc for 
    select * from (
        select t.*
               , row_number() over (partition by id order by whatever ) rn 
        from table_name t 
        where t.id in (List of ID`s)
     )
     where rn <= 3;

The whatever in the ROW_NUMBER() clause is the column you use to determine TOP-ness.