Question: I have a table in SQL Server 2005 which has three columns: 

```
id (int), 
message (text), 
timestamp (datetime)

```

There is an index on timestamp and id.

I am interested in doing a query which retrieves all messages for a given date, say '12/20/2008'. However I know that simply doing where timestamp='12/20/2008' won't give me the correct result because the field is a datetime field. 

Somebody had recommended using the DATEPART function and pulling the year, month, and day out of timestamp and verifying that these are equal to 2008, 12, and 20, respectively. It looks like this would not use the index I have on timestamp and would end up doing a full table scan.

So what is the best way to construct my query so that I am taking advantage of the index that I have created?

Answer: 
```
-- avoid re-calculating @MyDate +1 for every row
DECLARE @NextDay DateTime
Set @NextDay = @MyDate + 1

SELECT 
    -- ...
WHERE [timestamp] >= @MyDate AND [timestamp] < @NextDay

```
Assuming @Date is a datetime value for any datetime on the day you want all the messages for, use this

```
Where [timestamp] >= DateAdd(day, DateDiff(day, 0, @Date), 0) 
  And [timestamp] <  DateAdd(day, DateDiff(day, 0, @Date), 1) 

```

This is much faster than using a CAST, not to mention that when using CAST on datetimes, if you Cast a datetime value which is after noon to an integer, 

```
Declare @MyDate as Datetime
Set @MyDate = '12/25/2008 12:01:00'
Declare @IntVal Integer
Set @IntVal = Cast(@MyDate as Integer) 
Select Cast(@IntVal as DateTime)

```

it will round UP to the integer representing tne NEXT day's date. The above script will output 12/26/2008