In this chapter, you will see some familiar SQL commands with some surprising variations. SQL includes many subtleties that the discerning programmer can exploit. With better SQL, you can do more processing at the database and less processing in your application. By and large, this redistribution of labor will be better for the application and better for the database; it should also reduce the traffic between these components. In addition, by improving your SQL, you will make your queries easier to read.
Each main SQL engine has a command-line interface. Although such interfaces appear ancient, they are still essential utilities for all SQL hackers. Each interface has its own peculiarities, but they all do essentially the same job. You can find details of the command-line interfaces for SQL Server, Oracle, MySQL, Access, DB2, and PostgreSQL in "Run SQL from the Command Line" [Hack #1].