Should I index my sort fields in MySQL

Question

I have a field called 'sort_order' and it's bigint, i use it in my mysql queries for sorting.

Is it wise I put an index on it?

Answer 1

Generally, yes. If you are doing an ORDER BY on that field, it should probably be indexed. Of course you'll want to test it first to make sure it actually helps - if you only ever select a small number of rows it may not make that much of a difference.