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<Defensive database programming: SET vs. SELECT ⁄ >




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Comparing SET vs. SELECT is a very popular topic, and much of what I have to say has been said before. Assigning multiple values via SELECT performs better, and you don't have to repeat your code several times, as described by Tony Rogerson here and here. However, if you have ambiguities, SET will raise an error, but SELECT will not detect them, unless you use a smart trick described by Adam Machanic. Suppose, however, that you have a subquery that cannot have ambiguities at the time when you are developing it. For example, consider the following table and script:



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