Question

Imagine a table that has two fields, a smalltimedate and an int and about 1000 rows of data. What I’m attempting to do in query is to find the average of the INT field for rows between 3/3/2010 – 3/13/2010 and only if the entry is between 6:00am – 11:00pm.

I tried

between '2010-03-03 06:00 AND 2010-03-13 23:00'

However that only restricts that very beginning and end times. I could do this with a loop but I’m going to need to have the same query run over much larger date ranges and this will quickly eat server resources. Is there a way to query date and time separately?

Answer 1

Select ...
From Table
Where DateCol >= '20100303'
    And DateCol < '20100314'
    And DatePart(hh,DateCol) Between 18 And 23

Note that I use strictly less than in the comparison to 20100314 so it returns anything before 2010-03-14 midnight.

EDIT Realized you said PM and not AM.

ADDITION In SQL, the statement “Foo Between DateA And DateB” is translated into “Foo >= DateA and Foo <= DateB”. Notice the second part of that statement is less than or equal to to DateB. In our query, we want to include everything on 2010-03-13 all the way through midnight. I achieve that by restricting my search to values strictly less than the day after I want to search.

With respect to the hour, DatePart(hh, DateVal) will return the hour of the day using the 24 hour clock. So 6 PM is really 18:00 hours. If we want between 6 PM and 11 PM we really want between 18:00 and 23:00.

ADDITION It occurs to me that there is a small problem in my original solution. The system will return values whose time is anywhere during the 11 o’clock hour (e.g. 11:01 PM, 11:30 PM, 11:50 PM etc.). Here is another solution that would solve that:

Select ...
From Table
Where DateCol >= '20100303'
    And DateCol < '20100314'
    And DateAdd(day, -DateDiff(Day, 0, [DateCol]), [DateCol]) Between '18:00' And '23:00'

Basically, I’m using the DateDiff and DateAdd functions to strip off the Date portion of the value and then compare against the values we want.