How to Efficiently Retrieve All Dates Between Two Dates in SQL Server?

Tricks to get all dates between two dates in SQL Server

In SQL Server, getting all dates within a specified date range is useful for tasks such as data analysis, date processing, and record saving. This article will introduce several methods to efficiently obtain a sequence of consecutive dates between two given dates.

Use recursive common table expressions (CTE)

One way is to use recursive CTE. An example is as follows:

<code class="language-sql">;with GetDates As
(
    select DATEADD(day,1,@maxDate) as TheDate
    UNION ALL
    select DATEADD(day,1, TheDate) from GetDates
    where TheDate < @minDate
)
select TheDate from GetDates</code>

However, while this CTE works for selecting dates, it becomes difficult due to compilation errors when trying to store the results into a cursor.

Alternative methods

To increase efficiency and simplify operations, consider the following alternatives:

1. Use date table

If you create a date table in advance, the query becomes very simple:

<code class="language-sql">DECLARE @MinDate DATE = '20140101',
        @MaxDate DATE = '20140106';

SELECT  Date
FROM    dbo.Calendar
WHERE   Date >= @MinDate
AND     Date <= @MaxDate;</code>

2. Generate date sequence without date table

If you don’t have a date table, you can dynamically generate a date sequence using the following technique:

<code class="language-sql">DECLARE @MinDate DATE = '20140101',
        @MaxDate DATE = '20140106';

SELECT  TOP (DATEDIFF(DAY, @MinDate, @MaxDate) + 1)
        Date = DATEADD(DAY, ROW_NUMBER() OVER(ORDER BY a.object_id) - 1, @MinDate)
FROM    sys.all_objects a
        CROSS JOIN sys.all_objects b;</code>

3. Avoid using cursors for date iteration

It is generally recommended to avoid using cursors for date iteration. Collection-based approaches are generally more efficient and scalable. For example, if you want to retrieve the quantity for a specific date, you can use the following query:

<code class="language-sql">SELECT  TOP 1 date, it_cd, qty
FROM    T
WHERE   it_cd = 'i-1'
AND     Date = '20140101';</code>

By avoiding the use of cursors and leveraging these alternative techniques, you can efficiently retrieve all dates within a specified range in SQL Server.

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