Beginning SQL?

$ynergy writes "I have been seeing more and more job listings for SQL programmers so, naturally, my interest as been sparked. I have picked up a few materials but, soon realized that it would be easier to apply if I had experience using database software. Would everyone agree? So I am looking for resources, online or in print, that would give a beginner a real in depth look at using database SW." There are at least two issues here: a) learning standard SQL (pick a standard, any standard :) and b) learning all the idiosyncracies of a particular database system. Probably learning basic SQL is the way to start.

Comments

Much more complex than it first seems

[coyote-san]

This issue is a *lot* more complex than it first seems. There's a lot of really bad SQL code out there, and many of the authors don't even realize how little they know.

The problem is that it takes time and experience to really develop a sense for how to use the data. If you're a programmer, you should have at least some familiarity with performance issues even if you don't always pick the best algorithm for the problem. Likewise with a SQL database you really need to understand why 3NF is important, why referential integrity is a really good idea, etc. It's not uncommon for databases to span many gigabytes and a bad design can literally cost millions of dollars as you throw more hardware and expensive database licenses at the problem.

This isn't just theoretical - ghosting can be a problem with 3NF data, and you need to know how to recognize it and fix it. (More precisely, how to fix it without using 1NF or 2NF, which both have serious problems that 3NF fixes.)

Then there's the issues of views. It's easy to understand read-only views, but updateable views make life incrediby interesting. But this is critical - a bad updateable view will create a lot of subtle errors in your database.

Other issues - how do you access the data? This is everything from JDBC or Pro*C to JSP tag libraries. How do you handle bad data, or bad assumptions? (Nothing teaches you how hard it is to get a unique identifier like trying to actually find unique identifiers for real data.)

Finally, many of these sites aren't just looking for SQL knowledge, they're looking for specific packages like Oracle Financials.

I think the best way to illustrate just how much there is to learn is that a friend recently decided to get Oracle certification to help land jobs. She's been focusing on databases for almost a decade, yet she still had to study hard for the exams. I've been doing intermittent database work for even longer and have pulled several rabbits out of my hat - yet I know I would struggle to pass just one part (of four) of the exams.

But on the question at hand, my advice is to get an introductory text and start solving some problems. Create a database listing your CDs, then extend it to handle DVDs and VHS tapes, then extend it again to handle books and magazines. Create an index to keep track of your softball or bowling league stats - the teams, the players, the individual and team stats. You'll learn more from one or two reasonably large problems than you'll learn from a dozen books.