Querying many values from database by mutiple column

Question

I have following query:

SELECT
  a, b, value
FROM
  table
WHERE
  a = :a AND b = :b

I have to select a value for N=10000+ different (a, b) pairs.

The most simple solution is to make N single queries, but it sucks from the performance POV. What is more optimal solution for this case?

Answer 1

SELECT
  a, b, value
FROM
  table
WHERE
  (a ,b) in ((a1,b1),(a2,b2),(a3,b3),(a4,b4),(a5,b5)...(an,bn)) 

Answer 2

As you can't create a temporary table, maybe using a CTE instead ?

WITH cte AS ( SELECT 'a1' a, 'b1' b FROM DUAL
              UNION ALL SELECT 'a2' a, 'b2' b FROM DUAL
              UNION ALL SELECT 'a3' a, 'b3' b FROM DUAL
              ..
)
SELECT * FROM T JOIN cte USING (a,b)

I don't remember having used a 10000+ rows CTE though (probably not event in the 1000s). I don't know if this scale wells. Anyway, as about performances, without a proper index you probably can't really hope for something blazing fast.

---

As a matter of fact, I've just tested it on Oracle XE 11g: you can use a cte with more than 10000 rows. It works. But so sloooowly ... at least on my home test system.