Last 5 weeks prior to the last week in SQL - sql

Question

I want to take the last 5 weeks prior to the week before the current week. Today is Oct 4, 2017 so I want date range to be between Aug 21-Sep 24. This is the code I'm using, but it doesn't work for some reason:
DATEADD(week, -5, GETDATE()) and DATEADD(week, -1, GETDATE())
I also tried DATEADD(week, -6, GETDATE()) and DATEADD(week, -2, GETDATE()) but no change happens, so weird.
Can anyone help me please. It's sql query in SQL 2012.
WHERE hire_date between DATEADD(week, -6, GETDATE()) and DATEADD(week, -2, GETDATE())

Answer 1

Look at each of the expressions individually. Use Management Studio (or similar) to run just this:
SELECT DATEADD(week, -1, GETDATE())
And you'll see something like this (relative to the time when you run it):
2017-09-27 15:05:39.453
That's exactly one week ago, which was still a Wednesday. You want Sunday, the start of that week. So now do this:
SELECT DATEADD(week, DATEDIFF(week, 0, GETDATE()) -1, 0)
Which gives you this result:
2017-09-25 00:00:00.000
Closer. It works by taking day 0 and adding one less than the number of weeks that have passed since the week from your target date. You're adding whole weeks, and so you end up with a predictable whole-week start. You get the 25th (Monday) instead of the 24th because day 0 (Jan 1 1900) happened to be a Monday. But it's reliably a Monday, and easy enough now to account for the one more day:
SELECT DATEADD(DAY, -1, DATEADD(week, DATEDIFF(week, 0, GETDATE()) -1, 0))
And now we have a date you can use, from an expression that will consistently get it right:
2017-09-24 00:00:00.000
Sort of. You do need to carefully test how this behaves if run on Sunday or Monday, especially as Sql Server has a configurable start-of-week value. You may find you've crossed one fewer or greater week boundaries than you expect and end up with weird off-by-one errors. But even if that happens, this approach puts you on the path you need to walk.
For the other end, just change the number of weeks:
SELECT DATEADD(week, DATEDIFF(week, 0, GETDATE()) -6, 0)
To get this:
2017-08-21 00:00:00.000
Since the question asked for the Monday instead of Sunday we get skip the extra DATEADD() from before.
Now put it all together like so:
WHERE hire_date between
DATEADD(week, DATEDIFF(week, 0, GETDATE()) -6, 0)
AND
DATEADD(DAY, -1, DATEADD(week, DATEDIFF(week, 0, GETDATE()) -1, 0))

Answer 2

From what you're saying I think you need the first day of the earliest week to the last day of the latest week. To achieve this, you can do this:
WHERE hire_date between DATEADD(week, -6, DATEADD(WEEK, DATEDIFF(wk,0,GETDATE()), 0))
and DATEADD(week, -2, DATEADD(WEEK, DATEDIFF(wk,5,GETDATE()), 6))

Answer 3

DATEADD(week, -5, GETDATE()) substracts 30 days. You are going to have to do some manual DATEADD to get it to the beginning of the week, which is what it sounds like you're trying to do.
DECLARE #date datetime = GETDATE()
DECLARE #dw nvarchar = DATENAME(dw, #date)
IF #dw = 'Monday' SET #date = DATEADD(day, -1, #date)
ELSE IF #dw = 'Tuesday' SET #date = DATEADD(day, -2, #date)
....
WHERE hire_date between DATEADD(week, -6, #date) and DATEADD(week, -2, #date)
This way, you can set the beginning of the week yourself without having to be dependent on system culture.