Given a composite index on (a, b, c), which query can use the index?
- A WHERE b = 1
- B WHERE c = 1
- C WHERE a = 1 AND b = 2
- D WHERE b = 1 AND c = 2
Answer
WHERE a = 1 AND b = 2
A composite index can only be used from the leftmost column onwards. Skipping the leading column makes the index unusable for that predicate.





