Order of index on multiple columns

Question

Just a simple question, but does the order of your index matter when it spans over multiple columns?

For example, taking the query:

SELECT * FROM my_table WHE         


        

Answer 1

The best way to find out is to measure it. Try one, measure the performance, then remove that index and try the other. Typically you want data that is queried together to lie close together in the index on the disk, and the order of the columns in the index makes a difference to the way the index is stored on disk. It's very difficult to guess exactly what combination of indexes will work best, so try a few different possibilities and measure to find out which is best for your data.