Horrible JDBC Code and What's Wrong With It
Ah, Efficiency: Thou art a goddess who deserves worship, adulation, sacrifice, but thou art also a goddess who gets said worship, adulation, and sacrifice in all the wrong ways. Here's some JDBC code validating a login, trying to be good code (I think!)... that gets it wrong in almost every way possible.
Are JDBC statements portable across databases?
Ah, JDBC. Sometimes, people want to write JDBC code, because SQL is friendly and safe; then they discover that they actually don't want to deploy on MySQL after all, and they run into problems. The question is usually formed in this way: "If I write my SQL in a prepared statement, is it going to work the same way in $OTHER_DATABASE?"