[eluser]voidstar[/eluser]
If cache is enabled and a query merely contains the substring 'select' (e.g. the value of a field contains the word 'Selected'), DB_driver query() will check the cache, which includes testing whether the cache directory exists, the directory is writable, and attempting to read the cache file. These operations are expensive, and even though they'll fail for a false SELECT, it would be better not to perform them unnecessarily.