Question

Given a table with columns A,B,D,E,F.
I have two queries:

• one that orders by A then B.
• one that orders by A, then B, then C

I want to add an index on (A,B,C) to speed up the second query.
I’m thinking this will also speed up the first query. Is that correct? Or should I add a second index on (A,B)?

Or am I oversimplifying the problem of performance-tuning here?

Answer 1

Just put an index on all three of them. You don’t need a second index.