How to Efficiently Count Records Within a Date Range in SQL?

Calculating Record Counts for Dates Between Two Dates

To compute the number of records falling within a date range for a multi-axis chart, we must overcome the operand type mismatch in the original query. To address this issue, we explore alternative approaches that leverage tally tables or functions.

One highly performant solution involves utilizing a tally table or function. Itzik Ben-Gan's renowned tally function can be incorporated as follows:

DECLARE @StartDate date = '2020-11-01', @EndDate date = '2021-02-22';

  WITH
    L0 AS ( SELECT 1 AS c 
            FROM (VALUES(1),(1),(1),(1),(1),(1),(1),(1),
                        (1),(1),(1),(1),(1),(1),(1),(1)) AS D(c) ),
    L1 AS ( SELECT 1 AS c FROM L0 AS A CROSS JOIN L0 AS B ),
    L2 AS ( SELECT 1 AS c FROM L1 AS A CROSS JOIN L1 AS B ),
    Nums AS ( SELECT ROW_NUMBER() OVER(ORDER BY (SELECT NULL)) AS rownum
              FROM L2 )
    Date_Range_T (d_range) AS (
      SELECT TOP(DATEDIFF(day, @StartDate, @EndDate) + 1)
          DATEADD(day, rownum - 1, @StartDate) AS d_range,
          DATEADD(day, rownum, @StartDate) AS d_rangeNext
      FROM Nums
    )
SELECT d_range, COUNT(Id) AS Total 
FROM Date_Range_T 
LEFT JOIN tbl_Support_Requests R
    ON R.CreatedDate >= T.d_range AND R.CreatedDate < T.d_rangeNext
GROUP BY d_range
ORDER BY d_range ASC

This approach generates a date range table for the specified period, which is then used in a left join with the tbl_Support_Requests table to count records within each date range.

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