How to get the first day of a half year in SQL?

Question

To get the last day of a semester, I am using the below query:

select dateadd(quarter, datediff(quarter, 0, @mydate) / 2 * 2 + 2, -1)

I want to use a similar approach to get the first day of half year based on a given date.

For example, if my date is 5th of March 2024, then the SQL should return 1st of January 2024.
And if my date is 15th of November 2024. then the SQL should return 1st July 2024. Any help please?

Use a calendar table instead of trying to calculate dates on the fly. The expression you used may work but can't take advantage of any indexes. Using it for filtering and grouping quickly results in unreadable queries. With a calendar table though, all you have to do is to use the Semester, Quarter or HalfYear field — Panagiotis Kanavos
– Panagiotis Kanavos, Commented Feb 26, 2024 at 9:02

Thom A · Accepted Answer · 2024-02-26 10:32:04Z

2

The simplest method, in modern versions of SQL Server, would be to just use DATE_BUCKET:

SELECT DATE_BUCKET(MONTH, 6, GETDATE());

If you aren't on 2022+, you'll need to use the "old" DATEADD/DATEDIFF method. The /6 * 6 makes use of integer division. So, for example, 10 / 6 * 6 = (10 / 6) * 6 = (~1.66 ≈ 1) * 6 = 1 * 6 = 6

SELECT DATEADD(MONTH, DATEDIFF(MONTH, 0, GETDATE()) / 6 * 6,0);

edited Feb 26, 2024 at 10:32

answered Feb 26, 2024 at 8:59

Thom A♦

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2 Comments

Chin Over a year ago

Unfortunately the version which I am using does not have DATE_BUCKET.

Thom A Over a year ago

I've added the "old" way, but you should really denote the version you are using in your question, @Alis . This means you don't get solutions you can't use.

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