Question

Given this sample data set:

Date_Time
10/1/2011 12:05:00 AM
10/6/2011 2:25:00 AM
10/3/2011 5:59:00 AM
10/19/2011 6:01:00 PM
11/5/2011 8:30:00 PM
11/30/2011 11:59:00 PM

Is there a date time function in SQL server (2005 or 2008) that can count the number of records in these two time ranges? Below is the result from above data set.

Please let me know if a website that shows this as well.

Midnight-6:00am     6:00pm – Midnight. 
3                   3

Answer 1

Note, you want the second range to go up to 11:59pm, not midnight… Use DATEPART() to get just the hour portion of the dates and use the aggregate SUM() to add 1 to the total for each range when it is met. So what you need are hours between 0 and 5 (00:00 – 05:59) and 18 and 23 (18:00 – 23:59)

SELECT
  SUM(CASE WHEN DATEPART(hour, Date_Time) BETWEEN 0 AND 5 THEN 1 ELSE 0 END) AS  [Midnight to 6:00am],
  SUM(CASE WHEN DATEPART(hour, Date_Time) BETWEEN 18 AND 23 THEN 1 ELSE 0 END) AS  [6:00pm to 11:59pm]
FROM your_table

Update

The above counts up to 05:59:59am. If this really should count up to 06:00:00, you need to also check for the individual time parts for 6:00. This might be slow.

SELECT
  SUM(CASE WHEN
        DATEPART(hour, Date_Time) BETWEEN 0 AND 5 
        -- Look for 06:00:00 by stripping off the date portion and comparing against a character string
        OR (DATEPART(hour, Date_Time) = 6 AND DATEPART(minute, Date_Time) = 0 AND DATEPART(second, Date_Time) = 0)
      THEN 1 ELSE 0
      END
  ) AS [Midnight to 6:00am],
SUM(CASE WHEN DATEPART(hour, Date_Time) BETWEEN 18 AND 23 THEN 1 ELSE 0 END) AS  [6:00pm to 11:59pm]
FROM your_table

Alternatively, it might be faster to use

  SUM(CASE WHEN
        DATEPART(hour, Date_Time) BETWEEN 0 AND 5 
        -- Look for 06:00:00 also
        OR CONVERT(VARCHAR, Date_Time, 108) = '06:00:00'
      THEN 1 ELSE 0
      END
  ) AS [Midnight to 6:00am],