datetime fields and constarints

I've created a user defined datatype called t_date. It's a datetime datatype. I would like to bind a rule to the udt that constrains the time to 12:00am. Can anyone recommend the best way to do this.What about this?

create rule [myrule] as @.date=convert(varchar(10),@.date,101)+' 12:00'
GO|||Yep that works, in fact that's what I've been doing. I was hoping there was a more efficient way to check instead of having to cast to a string and back to a date again. It's not in your example but I cast back to a datetime to do the compare. Not sure if I have to or not.

Do you know how costly casting data in SQL server is?

Thanks for the help :-)|||It doesn't matter how costly it is, 'cause its the only way! You wants it, you pays for it!

blindman|||Thanx blindman, damn good thing my company has deep pockets because weez gonna have to pay|||Pay for processors...pay for memory...make sure they pay you good too!

Seriously, casting/converting datetime and string values is probably not a fast process, but for the string lengths you are dealing with it should not have a big impact on performance. And there is no way around it. MS Access, MS Excel, and other Microsquash products allow you to take the integer portion of the datetime value (a vast operation), but SQL Server uses a different logic for storing datetime values and this method won't work.

blindman