How can I get the last 12 months from the current date PLUS extra days till 1st of the last month retrieved

Question

Getting the last 12 months from a specific date is easy and can be retrieved by the following command in SQL-server. Its answer is 2014-08-17.

select Dateadd         


        

Answer 1

Using DATEADD and DATEDIFF:

DECLARE @ThisDate DATE = '20150817'
SELECT DATEADD(YEAR, -1, DATEADD(MONTH, DATEDIFF(MONTH, '19000101', @ThisDate), '19000101'))

For more common date routines, see this article by Lynn Pettis.

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To use in your WHERE clause:

DECLARE @ThisDate DATE = '20150817'
SELECT *
FROM 
WHERE
     >= DATEADD(YEAR, -1, DATEADD(MONTH, DATEDIFF(MONTH, '19000101', @ThisDate), '19000101'))