>>>Hi,
>>>
>>>I created a computed column in a table of SQL Server 2005. The column name is DaysOver. The formula in the Computed Column Specificaion is [Date1]-[Date2]. The type of the column is empty. Does this column always return an integer? Because I use it in the SQL select as following:
>>>
>>>

>>>select * from MyTable where DaysOver > 10
>>>

>>>
>>>And the returned query has the correct rows. But what if one of the DateTime columns (Date1 or Date2) is NULL? What will be returned?
>>
>>I hope you're using DATEDIFF function. The datediff function returns an integer. The type of derived column is determined by SQL Server itself and it may be tricky.
>>
>>You can also try adding CAST function if you want to ensure a specific type.
>
>As far as DATEDIFF, how would the syntax work? That is, if I want to replace the formula [Date1]-[Date2] with using DATEDIFF, what would the formula look like?
>
>Thank you.

If you want to return difference in Days, then the formula is

datediff(day, Date1, Date2).