Question

I have a table with timestamps. What is the proper query to get the records counts for each minute for the last hour.

I.e. if now is 2:25, I want to know how many record were between 1:25 and 1:26, 1:26 and 1:27, and so on, so I have 60 results.

Answer 1

This will return a count of results for each minute (where you have records) in the last hour

SELECT DATEPART(n, time_stamp) AS minute, COUNT(*) as results FROM table_name  WHERE time_stamp > DATEADD(hh, -1, GETDATE()) GROUP BY DATEPART(n, time_stamp) 

This may return less than 60 results, depending on the data. If you have to have 60 results, the query is slightly different. This uses a Common Table Expression to generate a list of 60 numbers and a correlated sub-query to get the results for each minute:

WITH numbers ( num ) AS (     SELECT 1 UNION ALL     SELECT 1 + num FROM numbers WHERE num < 60 ) SELECT num AS minute,     (SELECT COUNT(*) AS results     FROM table_name     WHERE DATEPART(n, time_stamp) = num     AND time_stamp > DATEADD(hh, -1, GETDATE()) FROM numbers 

To see the results, replace DATEADD(hh, -1, GETDATE()) with DATEADD(mi, -15, GETDATE()) and you’ll get the results for the last 15 minutes and 0 for other minutes.