The recommended method which Jack posted (where are ya, Jack?) will always run fast because the column in the WHERE clause on which it operates isn't subjected to any computation before it can be compared. This is significant whether or not the column is indexed, and more so if you're expecting the index to be used.
It baffles me to see code using a function on a column in a WHERE clause on a million-row table, when the computation could be applied - once - to the value which it's being compared to.
But you're correct Orion, Jack's method is specific for Datetime.
Cheers
ChrisM
For fast, accurate and documented assistance in answering your questions, please read this article.
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