Interesting article although it dwells more on C# than SQL. I too find Agile and Extreme Programming books fascinating but never found a way to make them useful in programming T-SQL.

Application and database programming are too different to treat the same and use XP techniques. Applications are snapshots of exe bytes. Developers only care about the final compile before release.

Database upgrades contain the entire evolution of changes between releases. The overwriting of new and improved stored procedures is the tiny part of the upgrade; the big part of upgrading is bringing the data up to the new schemata without loss or corruption.

Applications have objects and methods that have loose coupling and tightly defined interfaces. Stored procedures have parameters (interfaces) but they also access data directly (tight coupling to all tables and columns in a database) without going through a controlled interface. Because of this, I've always found it impossible to write test suites for sql.