Best way to check for current date in where clause of sql query

Question

I'm trying to find out the most efficient (best performance) way to check date field for current date. Currently we are using:

SELECT     COUNT(Job) AS Jobs
FROM         dbo.Job
WHERE     (Received BETWEEN DATEADD(d, DATEDIFF(d, 0, GETDATE()), 0)
                        AND DATEADD(d, DATEDIFF(d, 0, GETDATE()), 1))

Answer 1

WHERE
  DateDiff(d, Received, GETDATE()) = 0

Edit: As lined out in the comments to this answer, that's not an ideal solution. Check the other answers in this thread, too.

Answer 2

If you just want to find all the records where the Received Date is today, and there are records with future Received dates, then what you're doing is (very very slightly) wrong... Because the Between operator allows values that are equal to the ending boundary, so you could get records with Received date = to midnight tomorrow...

If there is no need to use an index on Received, then all you need to do is check that the date diff with the current datetime is 0...

Where DateDiff(day, received, getdate()) = 0

This predicate is of course not SARGable so it cannot use an index... If this is an issue for this query then, assuming you cannot have Received dates in the future, I would use this instead...

Where Received >= DateAdd(day, DateDiff(Day, 0, getDate()), 0) 

If Received dates can be in the future, then you are probably as close to the most efficient as you can be... (Except change the Between to a >= AND < )

Answer 3

If you want performance, you want a direct hit on the index, without any CPU etc per row; as such, I would calculate the range first, and then use a simple WHERE query. I don't know what db you are using, but in SQL Server, the following works:

// ... where @When is the date-and-time we have (perhaps from GETDATE())
DECLARE @DayStart datetime, @DayEnd datetime
SET @DayStart = CAST(FLOOR(CAST(@When as float)) as datetime) -- get day only
SET @DayEnd = DATEADD(d, 1, @DayStart)

SELECT     COUNT(Job) AS Jobs
FROM         dbo.Job
WHERE     (Received >= @DayStart AND Received < @DayEnd)