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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 am trying to get a month dates from the #EndDate including provided date (#EndDate) in SQ Server 2008.
#NoOfMonths is a variable which decides how much previous months dates we need.
e.g.
#EndDate = 2020-07-28
#NoOfMonths = 6
Expected result would be:
2020-07-28
2020-06-28
2020-05-28
2020-04-28
2020-03-28
2020-02-28
I am trying using below recursive CTE query, however the results are not expected, I am getting month end dates.
#EndDate: 2020-07-28
#NoOfMonths = 6
Result:
2020-07-31
2020-06-30
2020-05-31
2020-04-30
2020-03-31
2020-02-29
Code:
DECLARE #EndDate DATE = CAST('2020 - 07 - 28' AS DATE);
DECLARE #NoOfMonths INT = 6;
WITH CTE_previousMonths AS
(
SELECT
CAST(DATEADD(ss, -1, DATEADD(mm, DATEDIFF(m, -1, #EndDate), 0)) AS DATE) AS MonthPriorDate,
1 AS months
UNION ALL
SELECT
CAST(DATEADD(ss, -1, DATEADD(mm, DATEDIFF(m, 0, MonthPriorDate), 0)) AS DATE) AS MonthPriorDate,
months + 1 AS months
FROM
CTE_previousMonths
WHERE
months < #NoOfMonths
)
SELECT CTE_previousMonths.MonthPriorDate
FROM CTE_previousMonths;
Thanks!
I think this should do what you want:
with n as (
select 1 as n
union all
select n + 1
from n
where n < #NoOfMonths
)
select dateadd(month, 1 - n, #enddate)
from n;
Using Eomonth function:
WITH cte1 as
(
select EOMONTH('2020-07-28') as last_date, DATEADD(MONTH, -5, EOMONTH('2020-07-28')) AS END_DATE--Number of months - 1
union all
select DATEADD(MONTH, -1, last_date), END_DATE FROM CTE1 WHERE LAST_DATE > END_DATE
)
SELECT last_date FROM cte1;
In SQL Server I need to generate a table of Mondays up to the current date.
The starting date is always 2020-04-27, which is a Monday.
For example, if today is 2020-05-25, I need a table like below:
date
0 2020-04-27
1 2020-05-04
2 2020-05-11
3 2019-05-18
4 2019-05-25
If today's date is 2020-05-23, then it's:
date
0 2020-04-27
1 2020-05-04
2 2020-05-11
3 2019-05-18
How I can produce the table like that?
You can use a recursive CTE to generate the list of dates:
WITH mondays AS (
SELECT CAST('2020-04-27' AS date) AS monday
UNION ALL
SELECT DATEADD(WEEK, 1, monday)
FROM mondays
WHERE DATEADD(WEEK, 1, monday) <= GETDATE()
)
SELECT *
FROM mondays
Output:
monday
2020-04-27
2020-05-04
2020-05-11
2020-05-18
Demo on dbfiddle
Note that if you want to generate a list of more than 100 dates, you will need to increase the maximum recursion level (which defaults to 100). This can be done by adding OPTION (MAXRECURSION 0) to the end of the query i.e.
SELECT *
FROM mondays
OPTION (MAXRECURSION 0)
Use master..spt_values this default table to attain this
DECLARE #DATEFROM DATE ='2020-04-27',
#DATETO DATE= '2020-05-25'
SELECT ALLDATES AS MONDATES FROM
(SELECT DATEADD(D, NUMBER, #DATEFROM) AS ALLDATES FROM MASTER..SPT_VALUES
WHERE TYPE = 'P' AND NUMBER BETWEEN 0 AND DATEDIFF(DD, #DATEFROM, #DATETO)) AS D1
WHERE DATENAME(DW, D1.ALLDATES)IN('MONDAY')
I am looking for some T-SQL code that should pick the date which is "One Year back from current date (at the same time last Sunday in the month of January)".
For example:
Current day expected result
2017-02-05 2016-01-31
2017-01-05 2015-01-25
2018-02-19 2017-01-29
2018-01-19 2016-01-31
2019-02-28 2018-01-28
Please note: The year starts from last Sunday in January
I have some T-SQL code which is being used in SQL Server 2014:
select
convert(varchar(10), DATEADD(day, DATEDIFF(day, '19000107', DATEADD(month, DATEDIFF(MONTH, 0, CONVERT(date, CONVERT(VARCHAR(4), (CASE WHEN MONTH(GetDate()) = 1 THEN CONVERT(VARCHAR(4), GetDate(), 112) - 1 ELSE CONVERT(VARCHAR(4), GetDate(), 112) END), 112) + '0101')), 30)) / 7 * 7, '19000107'), 120)
The above code picks the date for current year's (last Sunday in January month). But I want T-SQL code to pick last year's (last Sunday's date in January month) date.
In detail - I want T-SQL code to produce expected result from below table
Current day T-SQL code answer expected result
2017-02-05 2017-01-29 2016-01-31
2017-01-05 2016-01-31 2015-01-25
2018-02-19 2018-01-28 2017-01-29
2018-01-19 2017-01-29 2016-01-31
2019-02-28 2019-01-27 2018-01-28
Any help please.
The best thing for this question is a numbers and date table. This answer shows you how to create one. Such a table is very handsome in many situations...
If I understand this correctly, you want the last Sunday in January of the previous year in all cases? Try this:
DECLARE #dummy TABLE(ID INT IDENTITY,YourDate DATE);
INSERT INTO #dummy VALUES
('2017-02-05'),('2017-01-05'),('2018-02-19'),('2018-01-19'),('2019-02-28');
WITH Years AS
(
SELECT * FROM (VALUES(2010),(2011),(2012),(2013),(2014),(2015),(2016),(2017),(2018),(2019),(2020)) AS t(Yr)
)
,LastSundays AS
(
SELECT Yr AS TheYear
,DATEADD(DAY,(DATEPART(WEEKDAY,LastOfJanuary) % 7)*(-1),LastOfJanuary) AS LastSundayOfJanuary
FROM Years
CROSS APPLY(SELECT CAST(CAST(Yr AS VARCHAR(4)) + '0131' AS DATE)) AS t(LastOfJanuary)
)
SELECT *
FROM #dummy AS d
INNER JOIN LastSundays AS ls ON YEAR(DATEADD(YEAR,-1,d.YourDate))=ls.TheYear;
The result (I do not understand row 2 and 4 completely...)
ID YourDate TheYear LastSundayOfJanuary
1 2017-02-05 2016 2016-01-31
2 2017-01-05 2016 2016-01-31 <--Your sample data is different...
3 2018-02-19 2017 2017-01-29
4 2018-01-19 2017 2017-01-29 <--Your sample data is different...
5 2019-02-28 2018 2018-01-28
Hint You might need to introduce ##DATEFIRST into your calculations...
Here is a way to do it without a date table (which is still a good idea BTW). Tested on all your inputs and it delivers the correct output each time. Obviously you would refactor this a bit as it's longwinded, just to show each step.
/* The input date. */
DECLARE
#input DATE = '2019-02-28';
/* The input date less one year. */
DECLARE
#date_minus_one_year DATE = DATEADD(yy,-1,#input);
/* The year part of the input date less one year. */
DECLARE
#year_date_part INT = DATEPART(yy,#date_minus_one_year);
/* 31 Jan of the previous year. */
DECLARE
#prev_year_jan_eom DATE = CAST(CAST(#year_date_part AS VARCHAR(4))+'-01-31' AS DATE);
/* What day of the week is 31 Jan of the previous year? */
DECLARE
#previous_eom_dw_part INT = DATEPART(dw,#prev_year_jan_eom);
/* Offest 31 Jan to the previous Sunday, won't change if the 31st is itself a Sunday. */
DECLARE
#output DATE = DATEADD(dd,1 - #previous_eom_dw_part,#prev_year_jan_eom);
/* Input and output */
SELECT
#input input
,#output [output];
I didn't think of a way to do it without the conditional in a case. It also uses the trick of casting a numeric year value to a January 1st date.
select case
when
datepart(dayofyear, dt) >
31 - datepart(weekday, dateadd(day, 30, cast(year(dt) as varchar(4))))
then
dateadd(day,
31 - datepart(weekday, dateadd(day, 30, cast(year(dt) as varchar(4)))),
cast(year(dt) as varchar(4))
)
else
dateadd(day,
31 - datepart(weekday, dateadd(day, 30, cast(year(dt) - 1 as varchar(4)))),
cast(year(dt) - 1 as varchar(4))
)
end
from (values
('20100201'), ('20110301'), ('20120401'),
('20130501'), ('20140601'), ('20150701'),
('20160801'), ('20170901'), ('20181001')
) t(dt)
Just for fun (untested)
select
dateadd(week,
-52 * ceil(sign(datediff(day, dt, hs)) + 0.5),
js
)
from
(select <date> dt) as t
cross apply
(
select 31 - datepart(weekday,
datefromparts(year(dt), 1, 31) as js
) t2;
SELECT
convert(varchar(10), DATEADD(day, DATEDIFF(day, '19000107', DATEADD(month, DATEDIFF(MONTH, 0, CONVERT(date, CONVERT(VARCHAR(4), (CASE WHEN MONTH(DATEADD(year,-1,GetDate())) = 1 THEN CONVERT(VARCHAR(4), DATEADD(year,-1,GetDate()), 112) - 1 ELSE CONVERT(VARCHAR(4), DATEADD(year,-1,GetDate()), 112) END), 112) + '0101')), 30)) / 7 * 7, '19000107'), 120)
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