SELECT * FROM Users WHERE RegistrationDate >= '1/20/2009'. it will automatically convert the string '1/20/2009' into the DateTime format for a date of 1/20/2009 00:00:00. So by using >= you should get every user whose registration date is 1/20/2009 or more recent. Edit: I put this in the comment section but I should probably link it here as well. More @Wikipedia
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