[mc3]

I'm certainly not an expert - I did a great DB course about 15 years ago and then used the skills every now and then since. I might not be up on the latest. And I am more of a SQL Server person. BUT... the main thing I learn is view actual execution plans, and see what is actually happening before adding indexes (unless it's an 'obvious' index).

> The best person I knew told me to index if a column wasn't unique, but also wasn't something with only two or three choices.

Yeah I think this is too broad advice, and you need to understand what you want to achieve. Mentally, choosing indexes is like choosing whether to use a hashtable vs. for loop vs. binary tree etc in an algorithm in code. There is not golden rule or "always use a hashtable if there are 100 entries" type thing. You just need to figure it out on a case by case basis. And usually there are only 2-3 tables in your DB worth a lot of effort in figuring it out!