Related
I have an issue where I need to determine fiscal quarters, but won't always know the start/end dates for the quarters. They will, however, always be 3 months long. What I will know is the ending date of the current quarter, and what quarter and year that refers to. For example, I might be given:
Current Quarter: Q4
Current Year: 2021
Current Quarter End Date: 1/31/2021
How can I get the quarter for any other date? If any of those 3 values were to change, the query still needs to provide the quarter for any given date based on those 3 parameters.
I came up with the following, which puts the last 4 years into a temp table:
DECLARE #QuarterEnd DATE = '1/31/2022'
, #CurrentQuarter INT = 1
, #CurrentYear INT = 2022
, #Counter INT = 16
, #qs INT = 0
, #qe INT = 2
, #DateToTest DATE = '12/15/2021'
CREATE TABLE #Quarters (
StartDate DATE
, EndDate DATE
, Qtr INT
, Yr INT
)
WHILE #Counter <> 0
BEGIN
INSERT INTO #Quarters VALUES (
cast(DATEADD(MONTH, DATEDIFF(MONTH, 0, #QuarterEnd)-#qe , 0) as date)
, cast(DATEADD(MONTH, DATEDIFF(MONTH, -1, #QuarterEnd)-#qs, -1) as date)
, #CurrentQuarter
, #CurrentYear
)
SET #Counter = #Counter - 1
SET #qs = #qs + 3
SET #qe = #qe + 3
SET #CurrentQuarter = CASE WHEN #CurrentQuarter = 1 THEN 4 ELSE #CurrentQuarter - 1 END
SET #CurrentYear = CASE WHEN #CurrentQuarter = 4 THEN #CurrentYear - 1 ELSE #CurrentYear END
END
SELECT #DateToTest
, (SELECT CONCAT('Q', Qtr, ' ', Yr) FROM #Quarters WHERE #DateToTest BETWEEN StartDate and EndDate)
FROM #Quarters
However, this doesn't seem to be practical when I'm running queries that will return hundreds of thousands of records.
I suppose I can throw that into a function and call it with:
SELECT MyQuarter = dbo.MyQuarterFunction(#QuarterEnd, #CurrentQuarter, #CurrentYear, #DateToTest)
There has to be a more efficient way to do this. Any suggestions?
Just create a permanent table called Quarters.
CREATE TABLE dbo.Quarters
(
StartDate date,
QuarterNumber tinyint,
FiscalYear int,
NextQuarterStartDate AS (DATEADD(MONTH, 3, StartDate))
);
INSERT dbo.Quarters(StartDate, QuarterNumber, FiscalYear)
VALUES('20200201',1,2020),
('20200501',2,2020),
('20200801',3,2020),
('20201101',4,2020),
('20210201',1,2021),
('20210501',2,2021),
('20210801',3,2021),
('20211101',4,2021),
('20220201',1,2022),
('20220501',2,2022),
('20220801',3,2022),
('20221101',4,2022);
Now any time you are given a date (like GETDATE()) you can find the other information easily:
DECLARE #date date = GETDATE();
SELECT * FROM dbo.Quarters
WHERE #date >= StartDate
AND #date < NextQuarterStartDate;
Example db<>fiddle
If you need to support multiple fiscal calendars simultaneously, just add a column (like CalendarID or CompanyID or CustomerID).
And really, you don't even need a calendar or quarters table for this. You already have a table of clients, right? Just add a column to store what month their fiscal year starts. That's really all you need.
CREATE TABLE dbo.Clients
(
ClientID int NOT NULL CONSTRAINT PK_Clients PRIMARY KEY,
Name nvarchar(200) NOT NULL CONSTRAINT UQ_ClientName UNIQUE,
FiscalYearStart tinyint NOT NULL CONSTRAINT CK_ValidMonth
CHECK (FiscalYearStart BETWEEN 1 AND 12)
);
Now let's insert a few rows with some clients with different fiscal years:
INSERT dbo.Clients(ClientID, Name, FiscalYearStart)
VALUES(1, N'ClientFeb', 2), -- fiscal year starts in February
(2, N'ClientMay', 5), -- fiscal year starts in May
(3, N'ClientNormal', 1); -- fiscal year matches calendar
Now, yes, we need a function, but let's not do any while loops or counters or #temp tables.
CREATE FUNCTION dbo.GetLast16Quarters
(
#DateToTest date,
#ClientID int
)
RETURNS TABLE WITH SCHEMABINDING AS
RETURN
(
WITH n(n) AS
(
SELECT n = 1 UNION ALL
SELECT n + 1 FROM n WHERE n < 20
),
Last20Quarters(QuarterStart, FiscalYearStart) AS
(
SELECT QuarterStart = DATEADD(QUARTER, 1-n,
DATEFROMPARTS(YEAR(#DateToTest)+1, FiscalYearStart, 1)),
FiscalYearStart
FROM dbo.Clients CROSS JOIN n WHERE ClientID = #ClientID
),
Last16Quarters AS
(
SELECT TOP (16) QuarterStart,
y = YEAR(DATEADD(MONTH, 1-FiscalYearStart, QuarterStart))
FROM Last20Quarters WHERE QuarterStart < #DateToTest
ORDER BY QuarterStart DESC
)
SELECT QuarterStart,
QuarterEnd = EOMONTH(QuarterStart, 2),
FiscalYear = y,
QuarterNumber = ROW_NUMBER() OVER
(PARTITION BY y ORDER BY QuarterStart)
FROM Last16Quarters);
Then to call it:
DECLARE #DateToTest date = '20211215';
SELECT * FROM dbo.GetLast16Quarters(#DateToTest, 1);
Output:
QuarterStart
QuarterEnd
FiscalYear
QuarterNumber
2018-02-01
2018-04-30
2018
1
2018-05-01
2018-07-31
2018
2
2018-08-01
2018-10-31
2018
3
2018-11-01
2019-01-31
2018
4
2019-02-01
2019-04-30
2019
1
2019-05-01
2019-07-31
2019
2
2019-08-01
2019-10-31
2019
3
2019-11-01
2020-01-31
2019
4
2020-02-01
2020-04-30
2020
1
2020-05-01
2020-07-31
2020
2
2020-08-01
2020-10-31
2020
3
2020-11-01
2021-01-31
2020
4
2021-02-01
2021-04-30
2021
1
2021-05-01
2021-07-31
2021
2
2021-08-01
2021-10-31
2021
3
2021-11-01
2022-01-31
2021
4
Example db<>fiddle
Assuming that you have two input variables:
declare #quarter_end date = '2021-01-31';
declare #current_quarter int = 4;
You can calculate the first month of financial year:
declare #first_month_of_fy int = (month(#quarter_end) - #current_quarter * 3 + 12) % 12 + 1;
-- 2 i.e. February
And use that value to calculate the quarter and year for any date using some math:
select *
from (values
('2020-12-15'),
('2021-01-15'),
('2021-12-15'),
('2022-01-15')
) as t(testdate)
cross apply (select
(month(testdate) - #first_month_of_fy + 12) % 12 + 1
) as ca1(month_of_fy)
cross apply (select
(month_of_fy - 1) / 3 + 1,
year(dateadd(month, 12 - month_of_fy, dateadd(day, - day(testdate) + 1, testdate)))
) as ca2(fy_quarter, fy_year)
DB<>Fiddle
I ended up creating a function to handle this. Since I'm given the last day of the quarter, which quarter it is, and which year it is, I can determine the start and end date of that fiscal year. Since a quarter is always 3 months, I can also determine which months fall into which quarter.
The first 4 variables, #qa, #qb, #qc, #qd hold a comma separated list of the months within each quarter (#qa is current quarter, #qb is current quarter -1, #qc is current quarter -2, and #qd is current quarter -3)
The second 2 variables determine the first day and last day of the fiscal calendar
To get the quarter & year, I first get the month from the supplied date (#Date) and see if it's in #qa, #qb, #qc or #qd. That tells me the fiscal quarter.
Finally, I compare the given date to the start and end date of the current fiscal year, and to the 6 years prior (going back 6 years is enough for what I need)
CREATE FUNCTION [dbo].[FunctionNameHere]
(
#Date DATE
, #QuarterEnd DATE
, #CurrentQuarter INT
, #CurrentYear INT
)
RETURNS VARCHAR(7)
AS
BEGIN
DECLARE #qa VARCHAR(8) = (concat(datepart(m, dateadd(m, 0, #QuarterEnd)),',', datepart(m, dateadd(m, -1, #QuarterEnd)),',', datepart(m, dateadd(m, -2, #QuarterEnd))))
DECLARE #qb VARCHAR(8) = (concat(datepart(m, dateadd(m, -3, #QuarterEnd)),',', datepart(m, dateadd(m, -4, #QuarterEnd)),',', datepart(m, dateadd(m, -5, #QuarterEnd))))
DECLARE #qc VARCHAR(8) = (concat(datepart(m, dateadd(m, -6, #QuarterEnd)),',', datepart(m, dateadd(m, -7, #QuarterEnd)),',', datepart(m, dateadd(m, -8, #QuarterEnd))))
DECLARE #qd VARCHAR(8) = (concat(datepart(m, dateadd(m, -9, #QuarterEnd)),',', datepart(m, dateadd(m, -10, #QuarterEnd)),',', datepart(m, dateadd(m, -11, #QuarterEnd))))
DECLARE #YearStart DATE = DATEADD(d, 1, DATEADD(q, -#CurrentQuarter, #QuarterEnd))
DECLARE #YearEnd DATE = DATEADD(q, 4-#CurrentQuarter, #QuarterEnd)
DECLARE #Qtr VARCHAR(8) = CONCAT('Q', CASE WHEN DATEPART(m, #Date) IN (SELECT value FROM string_split(#qa, ',')) THEN #CurrentQuarter
WHEN DATEPART(m, #Date) IN (SELECT value FROM string_split(#qb, ',')) THEN CASE WHEN #CurrentQuarter = 1 THEN 4
WHEN #CurrentQuarter = 2 THEN 1
WHEN #CurrentQuarter = 3 THEN 2
WHEN #CurrentQuarter = 4 THEN 3 END
WHEN DATEPART(m, #Date) IN (SELECT value FROM string_split(#qc, ',')) THEN CASE WHEN #CurrentQuarter = 1 THEN 3
WHEN #CurrentQuarter = 2 THEN 4
WHEN #CurrentQuarter = 3 THEN 1
WHEN #CurrentQuarter = 4 THEN 2 END
WHEN DATEPART(m, #Date) IN (SELECT value FROM string_split(#qd, ',')) THEN CASE WHEN #CurrentQuarter = 1 THEN 2
WHEN #CurrentQuarter = 2 THEN 3
WHEN #CurrentQuarter = 3 THEN 4
WHEN #CurrentQuarter = 4 THEN 1 END
END,
' ',
CASE WHEN #Date BETWEEN #YearStart AND #YearEnd THEN #CurrentYear
WHEN #Date BETWEEN dateadd(Year, -1, #YearStart) AND dateadd(Year, -1, #YearEnd) THEN #CurrentYear - 1
WHEN #Date BETWEEN dateadd(Year, -2, #YearStart) AND dateadd(Year, -2, #YearEnd) THEN #CurrentYear - 2
WHEN #Date BETWEEN dateadd(Year, -3, #YearStart) AND dateadd(Year, -3, #YearEnd) THEN #CurrentYear - 3
WHEN #Date BETWEEN dateadd(Year, -4, #YearStart) AND dateadd(Year, -4, #YearEnd) THEN #CurrentYear - 4
WHEN #Date BETWEEN dateadd(Year, -5, #YearStart) AND dateadd(Year, -5, #YearEnd) THEN #CurrentYear - 5
WHEN #Date BETWEEN dateadd(Year, -6, #YearStart) AND dateadd(Year, -6, #YearEnd) THEN #CurrentYear - 6
ELSE 9999 END)
return #Qtr
END
I know you can set #Date to 01/01/2001 as beginning of the month.
and then call dates that are first of every month, for example:
01/01/2001
01/02/2001
01/03/2001
but how would I please if possible is always find the date in the middle of the month? I would use 15th, but issue you have is with February
I need to make analysis of sum of sales mid month
any ideas please team
you can use this formula
DECLARE #Date DATE ='20180201'
SELECT DATEADD(DAY, (DAY(EOMONTH(#Date)) / 2) - 1, #Date)
Solution:
Get the count of the days in the month and calculate the "middle" day. In the next example the count of the days (28, 29, 30 or 31) is divided by an integer divisor (2), so the result will be an integer that has any fractional part truncated. Choose your preferred method.
DECLARE #date date
SET #date = DATEFROMPARTS(2020, 2, 1)
-- 15 is the half of the month with 30 and 31 days, 14 for months with 28, 29 days
SELECT DATEDIFF(d, #date, DATEADD(month, 1, #date)) / 2
-- 16 is the half of the month with 31 days, 15 for months with 29, 30 days, 14 for month with 28 days
SELECT (DATEDIFF(d, #date, DATEADD(month, 1, #date)) + 1) / 2
Example:
WITH Months AS
(
SELECT SomeDate = DATEFROMPARTS(2018, 1, 1)
UNION ALL
SELECT DATEADD(month, 1, SomeDate)
FROM Months
WHERE DATEPART(month, SomeDate) < 12
)
SELECT
SomeDate AS FirstDate,
DATEADD(d, -1, DATEADD(month, 1, SomeDate)) AS LastDate,
DATEDIFF(d, SomeDate, DATEADD(month, 1, SomeDate)) AS DaysBetween,
DATEDIFF(d, SomeDate, DATEADD(month, 1, SomeDate)) / 2 AS HalfOfMonth1,
(DATEDIFF(d, SomeDate, DATEADD(month, 1, SomeDate)) + 1) / 2 AS HalfOfMonth2
FROM Months
Output:
FirstDate LastDate DaysBetween HalfOfMonth1 HalfOfMonth2
01/01/2018 31/01/2018 31 15 16
01/02/2018 28/02/2018 28 14 14
01/03/2018 31/03/2018 31 15 16
01/04/2018 30/04/2018 30 15 15
01/05/2018 31/05/2018 31 15 16
01/06/2018 30/06/2018 30 15 15
01/07/2018 31/07/2018 31 15 16
01/08/2018 31/08/2018 31 15 16
01/09/2018 30/09/2018 30 15 15
01/10/2018 31/10/2018 31 15 16
01/11/2018 30/11/2018 30 15 15
01/12/2018 31/12/2018 31 15 16
i have tried the following
SELECT DATEADD(dd, (datediff(DD, DATEADD(m, DATEDIFF(m, 0, GETDATE()), - 1), eomonth(getdate())) / 2), DATEADD(m, DATEDIFF(m, 0, GETDATE()), - 1)),
CEILING((datediff(DD, DATEADD(m, DATEDIFF(m, 0, GETDATE()), - 1), eomonth(getdate())) / 2.00))
An update to the answer
DECLARE #Date DATE ='2018-10-01'---'20180201'
SELECT DATEADD(DAY, CEILING((DAY(EOMONTH(#Date)) / 2.00)) - 1, #Date)
Here is a query that get start date of month and end date of month by using datediff you can find the number of day to add and subtract
Set #tdate = '02/10/2018';
Select DATEFROMPARTS(YEAR(#tdate),MONTH(#tdate),1) as startdate , dateadd(day,-1,DATEFROMPARTS(YEAR(#tdate),MONTH(#tdate)+1,1)) as enddate
Regards
I have a SQL query that to return the number of items per week. I have a query that returns so far this:
Number of Items | Week Number
-------------------------------
100 | 18
80 | 19
120 | 20
And would like to return the following:
Number of Items | Week Beginning
-------------------------------
100 | 1st May 2017
80 | 8th May 2017
120 | 15th May 2017
What I have so far is:
SELECT COUNT(*) AS 'Number of Items', DATEPART(WEEK, Date) FROM table
where DATEPART(Year, Date) = '2017' and DATEPART(MONTH, Date) = 5
group by DATEPART(WEEK, Date)
You are talking about the 1st day of the current week:
example: select FORMAT(dateadd(ww,datediff(ww,0,getdate()),0),'dd MMM yyyy')--if you are using SQL 2012+
answer:
SELECT COUNT(*) AS 'Number of Items', FORMAT(dateadd(ww,datediff(ww,0,date_column),0),'dd MMM yyyy')
FROM table
where DATEPART(Year, Date) = '2017' and DATEPART(MONTH, Date) = 5
group by DATEPART(WEEK, Date)
As you need Monday to be the first day of the week
select DATEPART(WEEK, MyDate),DATEADD(DAY,1,(DATEADD(DAY, 1-DATEPART(WEEKDAY, MyDate), MyDate)))
from (
select '5/3/2017' MyDate
union all select '5/10/2017'
union all select '5/14/2017')A
SELECT DATEADD(DAY, DATEDIFF(DAY, 0, Date) /7*7, 0) AS StartDateOfWeek
check this if it solves
DECLARE #WeekNum INT
, #YearNum char(4);
SELECT #WeekNum = 20
, #YearNum = 2017
-- once you have the #WeekNum and #YearNum set, the following calculates the date range.
SELECT DATEADD(wk, DATEDIFF(wk, 6, '1/1/' + #YearNum) + (#WeekNum-1), 6) AS StartOfWeek;
SELECT DATEADD(wk, DATEDIFF(wk, 5, '1/1/' + #YearNum) + (#WeekNum-1), 5) AS EndOfWeek;
thanks to http://www.sqlteam.com/forums/topic.asp?TOPIC_ID=185440
SELECT datediff(week, dateadd(week, datediff(week, 0, dateadd(month, datediff(month, 0, EntryDate), 0)), 0), EntryDate - 1) + 1 as week,
count(UserID) as balance
FROM table_points
where right(convert(varchar, EntryDate, 106), 8)='Mar 2015'
GROUP BY datediff(week, dateadd(week, datediff(week, 0, dateadd(month, datediff(month, 0, EntryDate), 0)), 0), EntryDate - 1) + 1
When i execute this query i get result for 4th and 5th week values but not for others week. Like
week balance
4 80
5 100
In first 3 weeeks there is no values in database so it will not showing the values . Can any one bring 0 value for 1st , 2nd and 3rd week.
I want result as
week balance
1 0
2 0
3 0
4 80
5 100
can any one help me out.
Create a calendar/date table, including all possible dates/weeks, and from there left join the table_points table.
If no data is present in table_points, it will return 0 for those weeks.
If no dates are present in a table, it's impossible to select these and get a zero.
Example:
SELECT d.week, count(t.UserID)
FROM dates d left join table_points t on
d.date = t.EntryDate
where right(convert(varchar, d.date, 106), 8)='Mar 2015'
group by d.week
A date table can be very useful for many applications and could be filled like:
date week year month WeekOfMonth DayOfWeek Day Month
2015-03-01 18 2015 3 1 5 Friday March
2015-03-02 18 2015 3 1 6 Friday March
2015-03-03 18 2015 3 1 7 Sunday March
2015-03-04 19 2015 3 2 1 Monday March
This works like PSVSupporter's solution but uses a CTE to get a date list instead of using another table:
;WITH Dates AS (
SELECT
[Date] = CONVERT(DATETIME,'03/01/2015')
UNION ALL SELECT
[Date] = DATEADD(DAY, 1, [Date])
FROM
Dates
WHERE
Date < '03/31/2015'
)
SELECT
datediff(week, dateadd(week, datediff(week, 0, dateadd(month, datediff(month, 0, ds.Date), 0)), 0), ds.Date - 1) + 1 as week,
count(tp.UserID) as balance
FROM Dates ds
left join table_points tp on tp.EntryDate = ds.Date
WHERE right(convert(varchar, ds.Date, 106), 8)='Mar 2015'
GROUP BY datediff(week, dateadd(week, datediff(week, 0, dateadd(month, datediff(month, 0, ds.Date), 0)), 0), ds.Date - 1) + 1
I took CTE from https://stackoverflow.com/a/7824893/3309109
I am having a problem with week numbers. The customers week starts on a Tuesday, so ends on a Monday. So I have done:
Set DateFirst 2
When I then use
DateAdd(ww,#WeeksToShow, Date)
It occasionally gives me 8 weeks of information. I think it is because it goes over to the previous year, but I am not sure how to fix it.
If I do:
(DatePart(dy,Date) / 7) - #WeeksToShow
Then it works better, but obviously doesn't work going through to previous years as it just goes to minus figures.
Edit:
My currently SQL (If it helps at all without any data)
Set DateFirst 2
Select
DATEPART(yyyy,SessionDate) as YearNo,
DATEPART(ww,SessionDate) as WeekNo,
DATEADD(DAY, 1 - DATEPART(WEEKDAY, SessionDate + SessionTime), CAST(SessionDate +SessionTime AS DATE)) [WeekStart],
DATEADD(DAY, 7 - DATEPART(WEEKDAY, SessionDate + SessionTime), CAST(SessionDate + SessionTime AS DATE)) [WeekEnd],
DateName(dw,DATEADD(DAY, 7 - DATEPART(WEEKDAY, SessionDate + SessionTime), CAST(SessionDate + SessionTime AS DATE))) as WeekEndName,
Case when #ConsolidateSites = 1 then 0 else SiteNo end as SiteNo,
Case when #ConsolidateSites = 1 then 'All' else CfgSites.Name end as SiteName,
GroupNo,
GroupName,
DeptNo,
DeptName,
SDeptNo,
SDeptName,
PluNo,
PluDescription,
SUM(Qty) as SalesQty,
SUM(Value) as SalesValue
From
PluSalesExtended
Left Join
CfgSites on PluSalesExtended.SiteNo = CfgSites.No
Where
Exists (Select Descendant from DescendantSites where Parent in (#SiteNo) and Descendant = PluSalesExtended.SiteNo)
AND (DATEPART(WW,SessionDate + SessionTime) !=DATEPART(WW,GETDATE()))
AND SessionDate + SessionTime between DATEADD(ww,#NumberOfWeeks * -1,#StartingDate) and #StartingDate
AND TermNo = 0
AND PluEntryType <> 4
Group by
DATEPART(yyyy,SessionDate),
DATEPART(ww,SessionDate),
DATEADD(DAY, 1 - DATEPART(WEEKDAY, SessionDate + SessionTime), CAST(SessionDate +SessionTime AS DATE)),
DATEADD(DAY, 7 - DATEPART(WEEKDAY, SessionDate + SessionTime), CAST(SessionDate + SessionTime AS DATE)),
Case when #ConsolidateSites = 1 then 0 else SiteNo end,
Case when #ConsolidateSites = 1 then 'All' else CfgSites.Name end,
GroupNo,
GroupName,
DeptNo,
DeptName,
SDeptNo,
SDeptName,
PluNo,
PluDescription
order by WeekEnd
There are two issues here, the first is that I suspect you are defining 8 weeks of data as having 8 different values for DATEPART(WEEK, in which case you can replicate the root cause of the issue by looking at what ISO would define as the first week of 2015:
SET DATEFIRST 2;
SELECT Date, Week = DATEPART(WEEK, Date)
FROM (VALUES
('20141229'), ('20141230'), ('20141231'), ('20150101'),
('20150102'), ('20150103'), ('20150104')
) d (Date);
Which gives:
Date Week
-----------------
2014-12-29 52
2014-12-30 53
2014-12-31 53
2015-01-01 1
2015-01-02 1
2015-01-03 1
2015-01-04 1
So although you only have 7 days, you have 3 different week numbers. The problem is that DATEPART(WEEK is quite a simplistic function, and will simply return the number of week boundaries passed since the first day of the year, a better function would be ISO_WEEK since this takes into account year boundaries nicely:
SET DATEFIRST 2;
SELECT Date, Week = DATEPART(ISO_WEEK, Date)
FROM (VALUES
('20141229'), ('20141230'), ('20141231'), ('20150101'),
('20150102'), ('20150103'), ('20150104')
) d (Date);
Which gives:
Date Week
-----------------
2014-12-29 1
2014-12-30 1
2014-12-31 1
2015-01-01 1
2015-01-02 1
2015-01-03 1
2015-01-04 1
The problem is, that this does not take into account that the week starts on Tuesday, since the ISO week runs Monday to Sunday, you could adapt your usage slightly to get the week number of the day before:
SET DATEFIRST 2;
SELECT Date, Week = DATEPART(ISO_WEEK, DATEADD(DAY, -1, Date))
FROM (VALUES
('20141229'), ('20141230'), ('20141231'), ('20150101'),
('20150102'), ('20150103'), ('20150104')
) d (Date);
Which would give:
Date Week
-----------------
2014-12-29 52
2014-12-30 1
2014-12-31 1
2015-01-01 1
2015-01-02 1
2015-01-03 1
2015-01-04 1
So Monday the 29th December is now recognized as the previous week. The problem is that there is no ISO_YEAR built in function, so you will need to define your own. This is a fairly trivial function, even so I almost never create scalar functions because they perform terribly, instead I use an inline table valued function, so for this I would use:
CREATE FUNCTION dbo.ISOYear (#Date DATETIME)
RETURNS TABLE
AS
RETURN
( SELECT IsoYear = DATEPART(YEAR, #Date) +
CASE
-- Special cases: Jan 1-3 may belong to the previous year
WHEN (DATEPART(MONTH, #Date) = 1 AND DATEPART(ISO_WEEK, #Date) > 50) THEN -1
-- Special case: Dec 29-31 may belong to the next year
WHEN (DATEPART(MONTH, #Date) = 12 AND DATEPART(ISO_WEEK, #Date) < 45) THEN 1
ELSE 0
END
);
Which just requires a subquery to be used, but the extra typing is worth it in terms of performance:
SET DATEFIRST 2;
SELECT Date,
Week = DATEPART(ISO_WEEK, DATEADD(DAY, -1, Date)),
Year = (SELECT ISOYear FROM dbo.ISOYear(DATEADD(DAY, -1, Date)))
FROM (VALUES
('20141229'), ('20141230'), ('20141231'), ('20150101'),
('20150102'), ('20150103'), ('20150104')
) d (Date);
Or you can use CROSS APPLY:
SET DATEFIRST 2;
SELECT Date,
Week = DATEPART(ISO_WEEK, DATEADD(DAY, -1, Date)),
Year = y.ISOYear
FROM (VALUES
('20141229'), ('20141230'), ('20141231'), ('20150101'),
('20150102'), ('20150103'), ('20150104')
) d (Date)
CROSS APPLY dbo.ISOYear(d.Date) y;
Which gives:
Date Week Year
---------------------------
2014-12-29 52 2014
2014-12-30 1 2015
2014-12-31 1 2015
2015-01-01 1 2015
2015-01-02 1 2015
2015-01-03 1 2015
2015-01-04 1 2015
Even with this method, by simply getting a date 6 weeks ago you sill still end up with 7 weeks if the date you are using is not a Tuesday, because you will have 5 full weeks, and a part week at the start and a part week at the end, this is the second issue. So you need to make sure your start date is a Tuesday. The following will get you Tuesday of 7 weeks ago:
SELECT CAST(DATEADD(DAY, 1 - DATEPART(WEEKDAY, GETDATE()), DATEADD(WEEK, -6, GETDATE())) AS DATE);
The logic of this is explained better in this answer, the following is the part that will get the start of the week (based on your datefirst settings):
SELECT DATEADD(DAY, 1 - DATEPART(WEEKDAY, GETDATE()), GETDATE());
Then all I have done is substitute the second GETDATE() with DATEADD(WEEK, -6, GETDATE()) so that it is getting the start of the week 6 weeks ago, then there is just a cast to date to remove the time element from it.
This will get you current week + 5 previous weeks starting tuesday:
WHERE dateadd(week, datediff(d, 0, getdate()-1)/7 - 4, 1) <= yourdatecolumn
This will show examples:
DECLARE #wks int = 6 -- Weeks To Show
SELECT
dateadd(week, datediff(d, 0, getdate()-1)/7 - 4, 1) tuesday5weeksago,
dateadd(week, datediff(d, 0, getdate()-1)/7 - 5, 1) tuesday6weeksago,
dateadd(week, datediff(d, 0, getdate()-1)/7 - 6, 1) tuesday7weeksago,
dateadd(week, datediff(d, 0, getdate()-1)/7 - #wks + 1, 1) tuesdaydynamicweeksago
Result:
tuesday5weeksago tuesday6weeksago tuesday7weeksago tuesdaydynamicweeksago
2015-01-27 2015-01-20 2015-01-13 2015-01-20