Kevin Hill goes back to basics:
“What Is an Index?”
I get this question a lot, especially from developers and sysadmins who’ve been handed a SQL Server and told, “Keep it running fast.” No pressure.
Given that the percentage of people in this industry who have actually seen a phone book continually decreases, it’s for the best that Kevin didn’t use that worn-out example.
If you’re new to indexing in SQL Server, this is a good way to jump-start your knowledge. Then, you spend a while learning the exceptions to the rules and the foibles in existing systems.