I field the questions that come to our Ask the Expert section—deleting spam and nonsense and otherwise undesirable questions before forwarding the potentially answerable ones on to our panel of experts. I don’t have to answer them, and even I get annoyed when I see the same, often vague questions over and over (“How to back up my database?”) or something that obviously came from a homework assignment. (When you get 10 questions in a row from the same email address, all addressing different “problems,” it looks a little suspicious.)

That’s why I’m working on a collection of FAQ resources for our readers, so our experts won’t have to keep answering the same queries over and over again. One of our first new FAQ offerings is a three-part SQL FAQ assembled by our witty resident SQL guru Rudy Limeback. Rudy revisits the most common questions he’s taken over the past six years, from the most basic duh-type questions, to the homework questions, to genuinely complex and interesting ones. Check out all three parts of the FAQ:

• Part one: Novice questions: These are generally very simple and are asked by beginners who are quite unfamiliar with SQL. Common examples include “What is the difference between…” questions, such as “What is the difference between a candidate key and a composite key?” Other common novice questions depend on circumstances and context, such as “Which is faster, a subquery or a join?”
• Part two: Homework questions: Our experts are usually reluctant to answer these, but Rudy will take a homework question if it can teach something interesting like a subtle nuance of SQL to all readers. For example, “All employees under a given manager” is a common but tough problem that Rudy discusses comprehensively.
• Part three covers serious and complex SQL questions that come up frequently. This is the meatiest part of the FAQ, so dig in and enjoy! You’ll discover how to delete duplicate rows, how to find the first (or last) N rows in a table, how to handle pagination and much more.

If you’ve got a burning SQL question that’s not addressed here, send it to Rudy. He thrives on them.

-Elisa