Just a Theory

By David E. Wheeler

Learn Mad Database Skillz at YAPC::NA 2009

A few weeks ago, I twittered that, in my opinion, application developers should really learn how to use databases. And by that I mean SQL, really. I know that a lot of app developers like to use ORMs to access the database, so that you don’t have to really think about it, but most ORMs are written by people who don’t like databases, don’t like SQL, haven’t taken the time to learn it in any depth, and thus don’t write very good SQL. And even if they do like SQL, that usually means they provide a way for you to execute SQL queries directly. The reason? Because the ORM does not really understand how building more and more complex queries can have negative performance issues, and that there is more than one way to do it. It’s pretty common to have to go back to custom SQL to solve performance issues. So to solve those problems, you gotta understand SQL.

Another sin of application developers is to try to use very standard SQL syntax and features when writing SQL queries, so that they can easily be ported to other databases. Well, if you’re going to do that, you might as well use an ORM, but never mind. Think about it this way: If you were writing an application in Ruby, would you avoid the use of blocks because you might someday want to port it to Perl? And how often have you decided to port an application to another database, anyway? Sure, some OSS projects add support for new databases, but they seldom drop support for one RDBMS in favor of another.

If you’re writing an application in Perl, it pays to learn idiomatic Perl. If you’re writing it in Ruby, it pays to use idiomatic Ruby. So why would you settle for anything less when using an RDBMS? SQL is, after all, just another programming language, and the various dialects have their advantages and disadvantages. Learning how SQL really works and how to leverage the features of your RDBMS will only improve the performance, reliability, and scalability of your app. If your Perl or Ruby or Python code doesn’t look like C, why would you write least-common denominator ANSI-92 compliant SQL? You have a powerful programming language and application server with an amazing array of features and capabilities. Use them!

All of which is a very long-winded way to say that it really, truly pays to learn the ins and outs of SQL, just like any other language. And if you’re a Perl hacker, you have a great opportunity to do just that at YAPC::NA 10 this summer. In response to my tweet, YAPC organizer Robert Blackwell replied in agreement, and pointed out that famed SQL expert Joe Celko, author of numerous volumes on SQL syntax and techniques, will be offering two classes on SQL at YAPC:

This is a great opportunity to expand your knowledge of SQL, how it works, and why it’s so powerful. (Even if you’re not fond of the idea of relational databases, think of it as an opportunity to follow Tom Christiansen’s injunction and learn a bit about logical programming.) Celko knows SQL like nobody’s business, and will be sharing that knowledge in two remarkably cheap courses. Even if you’re not a Perl hacker, if you want to really learn the ins and outs of SQL– how to write idiomatic SQL to match the mad skillz you already apply to your application code, you could hardly do better than to get in on these deals and drink from the Celko firehose. I only wish I was going to be there (alas, prior plans interfered). But do please tell me all about it!

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