If you work with SQL — especially with Oracle — and you don’t read Ask Tom, you are missing a goldmine of tips and tuning advice. In the words of my former colleague Andy, “That Tom guy’s the shit.”

The best part of it is that Oracle pays him just to put his tips on the web, so we developers benefit. No login or payola required. Way to put developers first Oracle! Maybe Informatica could learn a few lessons from this.

Sometimes the best performance tips are those you don’t even think about. When to use UNION or UNION ALL. Most people will just use UNION unless they really need all the rows returned. You need to change this thinking. Use UNION ALL unless you know you need the duplicates filtered. Tom lays it out.

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