get 5th previous date from current date through SQL except public holiday - sql

Question

i need a sql function which has to return 5th previous business date except saturday sunday and public holiday,
Ex: i should get last thursday (04-01-2018) if i won't have any public holiday inbetween im able to achieve that by,
SELECT DATEADD(DAY, CASE DATENAME(WEEKDAY, GETDATE())
WHEN 'Sunday' THEN -2
WHEN 'Monday' THEN -3
ELSE -1 END, DATEDIFF(DAY, 5, GETDATE()))
but how to omit public holiday from this,
Can anyone help me please

Answer 1

If you don't want (or you can't) create a calendar "tally" table (with columns identifying holidays and week-end days) you can try a query like following one.
sample data for holidays table
CREATE TABLE HOL_TAB (DAT DATETIME);
INSERT INTO HOL_TAB VALUES ('2018-01-05');
INSERT INTO HOL_TAB VALUES ('2018-01-04');
The query use a CTE to "create" on the fly a small tally calendar table (I used 12 as limit, but you can change it).
The last SELECT use a join with holiday table to exclude those days and then ROW_NUMBER() to extract "first" five days.
To keep query similar to the one you made I used DATENAME, but I suggest to avoid its use and use instead other methods).
WITH CAL_TAB AS (
SELECT DATEADD(dd, 0, CAST(GETDATE() AS DATE) ) AS DAT
, 1 AS COUN
UNION ALL
SELECT DATEADD(dd, -1- CASE DATENAME (WEEKDAY, DATEADD(dd,-1,B.DAT) ) WHEN 'Sunday' THEN 2 WHEN 'Saturday' THEN 1 ELSE 0 END, B.DAT ) AS DAT
, B.COUN+1 AS COUN
FROM CAL_TAB B
WHERE B.COUN<12 /* 12 is just to limit number of days */
)
SELECT DAT, WD
FROM (SELECT C.DAT, C.COUN, DATENAME(WEEKDAY, C.DAT) AS WD, ROW_NUMBER() OVER (ORDER BY COUN) AS RN
FROM CAL_TAB C
WHERE NOT EXISTS(SELECT DAT FROM HOL_TAB D WHERE D.DAT=C.DAT)
) E WHERE RN<=5;
Output:
DAT WD
1 10.01.2018 00:00:00 Wednesday
2 09.01.2018 00:00:00 Tuesday
3 08.01.2018 00:00:00 Monday
4 03.01.2018 00:00:00 Wednesday
5 02.01.2018 00:00:00 Tuesday

Answer 2

try This Logic
WITH CTE
AS
(
SELECT
MyDate = DATEADD(DD,-5,GETDATE())
)
SELECT
MyDate = CASE WHEN DATENAME(WEEKDAY, MyDate) IN ('Sunday','Saturday')
THEN NULL
WHEN MHL.Holiday IS NOT NULL
THEN NULL
ELSE CTE.MyDate END
FROM CTE
LEFT JOIN MyHoliDayList MHL
ON CTE.MyDate = MHL.Holiday

Answer 3

Try this Method:
DECLARE #Holiday TABLE(HoliDay DATE)
INSERT INTO #Holiday VALUES ('2018-01-02')
INSERT INTO #Holiday VALUES ('2018-01-05')
DECLARE #WithOutHoliDay DATETIME = (SELECT DATEADD(DAY, CASE DATENAME(WEEKDAY, GETDATE())
WHEN 'Sunday' THEN -2
WHEN 'Monday' THEN -3
ELSE -1 END, DATEDIFF(DAY, 5, GETDATE())))
SELECT DATEADD(DAY,0-
(SELECT COUNT(1)
FROM #Holiday
WHERE HoliDay BETWEEN #WithOutHoliDay AND GETDATE()),#WithOutHoliDay)
This should give, what exactly you need...