Get the First Day of Current Week based on a given date variable

Question

How do I get the current week range in SQL based on a given date? Currently using the following query which provides an incorrect resultset.

Declare @dt date = '1994-08-27'
SELECT [start_of_week] = DATEADD(WEEK, DATEDIFF(WEEK, @dt, CURRENT_TIMESTAMP), @dt);

Please check the image for details of expected result set:

Answer 1

You could get the day of the week and use that to go back to the day you want (in this example Sunday).

In MySQL dialect that looks like:

SELECT DATE_SUB(NOW(),INTERVAL DAYOFWEEK(NOW())-1 DAY);

Sunday is day 1, so that is why the -1 is there. NOW() is just right now, so you can replace that with your own date easily.

Answer 2

To get the first day of current week, try this :

DECLARE @dt DATE = '1994-08-27'
SET @StartOfWeek = DATEADD(ww, DATEDIFF(ww, 0, @dt), 0)

Information : the first day of the week for 1994-08-27 is 1994-08-22.