Being a programmer foremost and group leader at one time, I can the say the interview question is junk. The best programmer I ever developed was an engineer graduate who didn't know how to program well at the time of hiring. I just saw his personal potential.

On the SQL world, there are some good authors but if I am forced to read only one in a day, I would read the articles of the very brilliant person: Itzik Ben-Gan of SQL Magazine.