Get yesterdays date and if Monday get weekend range for SQL server - sql

Question

How do I get yesterdays date and if the current date is Monday I would need Sunday, Saturday and Friday. This is already asked here for ms access. I now need this for SQL server. How would I go about this?
Will create an inline view that will return the previous date in SQL It will return between 1 and 3 rows depending on the current date.
If current date is Monday Return:
Sundays date
Saturdays date
Fridays date
If current date is Tuesday then Return: Mondays date
If current date is Wednesday then Return: Tuesdays date
If current date is Thursday then Return: Wednesdays date
If current date is Friday then Return: Thursdays date
If current date is Saturday then Return: Fridays date
If current date is Sunday then Return: Saturdays date
I hope this helps explain what I am trying to do more clearly.
sample select query
--get previous date
select * from [Purchase Orders] where MyDate in (previous date(s))

Answer 1

Not entirely clear about the question though. But you can do something on the similar lines.
Using DATEPART and DATEADD
DECLARE #TodaysDate DATETIME
SET #TodaysDate = '2013-04-10'
SELECT CASE
WHEN DATEPART (DW, DATEADD (DD, -1, #TodaysDate )) IN (1, 6, 7)
THEN 'WeekEnd' ELSE 'WeekDay'
END D

Answer 2

Using the query you linked to, you can try the code below:
SELECT *
FROM [Purchase Order]
WHERE MyDate >= CASE
WHEN DATENAME(dw, CONVERT(CHAR(8), GETDATE() , 112)) LIKE 'Monday' THEN CONVERT(CHAR(8), DATEADD(dd, -3, GETDATE()), 112)
ELSE CONVERT(CHAR(8), DATEADD(dd, -1, GETDATE()), 112)
END
AND MyDate < CONVERT(CHAR(8),GETDATE(),112)

Answer 3

You can use the following table function:
CREATE FUNCTION dbo.ufnPreviousDay (#suppliedDate DATE)
RETURNS #PreviousDates TABLE (PreviousDate DATE)
AS
BEGIN
INSERT INTO #PreviousDates (
PreviousDate)
SELECT
PreviousDate = DATEADD(DAY, -1, #suppliedDate)
IF DATEPART(WEEKDAY, DATEADD(DAY, ##DATEFIRST - 1, #suppliedDate)) = 1 -- If Monday
BEGIN
INSERT INTO #PreviousDates (
PreviousDate)
SELECT
PreviousDate = DATEADD(DAY, -2, #suppliedDate)
UNION ALL
SELECT
PreviousDate = DATEADD(DAY, -3, #suppliedDate)
END
RETURN
END
You can use it like this:
SELECT
T.*
FROM
dbo.ufnPreviousDay('2018-03-19') AS T
/*
Result:
2018-03-18
2018-03-17
2018-03-16
*/
If you want today's previous dates:
SELECT
T.*
FROM
YourTable AS T
INNER JOIN dbo.ufnPreviousDay(GETDATE()) AS M ON T.MyDate = M.PreviousDate