Question

I’m trying to select a set of dates that is closest to (including before and after) a specific date.

I’m pretty close, all I want to do now is select the top 10 ‘Closeness’ to 0… but I’m not sure how to do that.

BEGIN
Declare @DateCenter datetime2 = '2011-03-30 00:15:00'
Declare @DateStart datetime2 = DATEADD(day,-7,@DateCenter)
Declare @DateEnd datetime2 = DATEADD(day,7,@DateCenter)
SELECT TOP 30 *, DateDiff(hour, Utc, @DateCenter) as Closeness
FROM [CheckIns]
WHERE Utc BETWEEN @DateStart AND @DateEnd
END

Answer 1

10 or 30, you’re narrative and code sample don’t match. Anyhow, the following should work:

select top 10 *
from (
     select *,ROW_NUMBER() OVER (ORDER BY ABS(DATEDIFF(minute,Utc,@DateCenter))) as rn
     from CheckIns
) t
order by rn

this doesn’t distinguish between those before and those after – it simply seeks the 10 closest. If you wanted, say, the 10 that precede a date, and the 10 that succeed it, then you’d need 2 orderings, or possibly a PARTITION BY clause also to the ROW_NUMBER window function.

If you wanted to include tied results, you’d need to switch to using RANK() or DENSE_RANK() instead of ROW_NUMBER().