How to Efficiently Generate a List of Dates Within a Specified Range in a Database?

Date generation within database date range

In many database applications, it is often necessary to generate a date list within a specified date range. While there are multiple ways to do this, one efficient way is to utilize a subquery to generate a large number of dates and then filter based on the desired range.

The following scenario demonstrates this approach:

<code class="language-sql">select a.Date
from (
    select curdate() - INTERVAL (a.a + (10 * b.a) + (100 * c.a) + (1000 * d.a) ) DAY as Date
    from (select 0 as a union all select 1 union all select 2 union all select 3 union all select 4 union all select 5 union all select 6 union all select 7 union all select 8 union all select 9) as a
    cross join (select 0 as a union all select 1 union all select 2 union all select 3 union all select 4 union all select 5 union all select 6 union all select 7 union all select 8 union all select 9) as b
    cross join (select 0 as a union all select 1 union all select 2 union all select 3 union all select 4 union all select 5 union all select 6 union all select 7 union all select 8 union all select 9) as c
    cross join (select 0 as a union all select 1 union all select 2 union all select 3 union all select 4 union all select 5 union all select 6 union all select 7 union all select 8 union all select 9) as d
) a
where a.Date between '2010-01-20' and '2010-01-24'</code>

Instructions:

This subquery generates a large number of dates by combining values ​​from multiple columns. The curdate() function returns the current date and the INTERVAL clause subtracts from the current date the combination of numbers generated by the cross join of tables a, b, c and d. By varying these numbers, a wide range of dates can be generated.

Outer SELECT statement then filters the generated dates based on the specified date range. The result is a set of dates that fall within the range, starting with the most recent date.

Performance considerations:

This solution performs very well even when generating a large number of dates. Subqueries use cross joins and mathematical operations to efficiently generate dates without relying on loops or complex calculations.

Portability:

This technique is portable across most databases and requires only minor modifications to adapt to the syntax of a specific database.

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