I'm calculating the week for a specific date in SQL for example
'2016-01-20' (yyyy-mm-dd) but SQL returns week: 4, and that is wrong because this year the first week started on '2016-01-04' the result must be week: 3.
I think the issue is generatad because 2015 was a year with 53 weeks, any solution to that? Thank you and I'm sorry for my bad English
In tSQL the DATEPART() is returning the correct data based on US and Most of Europe as well as UK See here
You can use SET DATEFIRST to adjust the start position however.
The ISO 8601 definition for week 01 is the week with the year's first Thursday in it. I am using Intersystems cache which apparently does not account for that either. So I have used this to address that
CASE WHEN 7-datepart(dw,dateadd(dd,1,dateadd(yy,datediff(yy,0,getdate())-1,0))) < 2
THEN datepart(wk,getdate())-1 ELSE datepart(wk,getdate()) END as WeekNum
Related
I am creating a forecast of orders for the year 2021 and breaking it out by week.
I am using
SELECT DATEPART(WK,'2021-01-01')
to find my weeks however i am running into an issue where 2021-01-01 through 2021-01-03 actually fall into week 53 of year 2021. is there a way i can tell sql to mark those dates as week 53 and start on the 4th as week 1?
I think you are looking for the "iso_week" option on datepart():
select datepart(iso_week, '2021-01-01')
Getting the ISO year, unfortunately, is trickier, but that is not your question.
For my project I need to have an absolute numerical correspondence between days of the week and 1...7 values.
As you probably know the association between days and numbers can vary according to the locale, for example in Germany Monday is 1 and Sunday is 7, while in US Monday is 2 while Sunday is 1.
So, searching for a solution, I found the following code which seems working regardless of the locale, assigning Monday=1...Sunday=7:
1 + TRUNC (date) - TRUNC (date, 'IW')
Can someone explain me how does it work? In particular I just can't understand what this instruction:
TRUNC (date, 'IW')
exactly does.
TRUNC(DATE,'IW') returns the first day of the week. For me TRUNC(SYSDATE,'IW) returns Monday. Today is Tuesday Feb 21. Subtract from that TRUNC(SYSDATE,'IW') which would be Monday the 20th, and you'll get 1 (because 21-20=1). Add 1 onto that as you do in the beginning of your equation and you get 2, which we associate with Tuesday.
The very basic concept of ISO week is to make it NLS territory independent.
From documentation,
Week of year (1-52 or 1-53) based on the ISO standard.
A week starts on a Monday and ends on a Sunday.
I'm pretty new to SQL so I hope this isn't a dumb question, tried to google but couldn't find anything.
I'm summing sales of departments per week in SQL and am using TD_SYSFNLIB.WEEKNUMBER_OF_YEAR (trans_dt) to get the week number.
I think everything is working except I'd like to change the format of the weeks to the start date of the week, e.g. week 1 = 1/4/15
Also, i'm not sure how to handle the very first of the year week 0 since I think that should be grouped up with week 52 of last year.
The following date math trick should get you Beginning of Week as an actual date without having to join to the SYS_CALENDAR view or using a function:
SELECT CURRENT_DATE - ((CURRENT_DATE - DATE '0001-01-07) MOD 7) AS BOW;
Starting with TD14 there's NEXT_DAY which returns the following weekday, if you subtract 7 days you get the previous day:
next_day(trans_dt - 7, 'sunday')
I'm looking for a way to convert an ISO date to Month and I also need to covert an ISO week to Month.
I need to do this in Excel and Access.
I found this formula for excel but when converting it to Access it does not work. Is there a simple way to accomplish this?
I found this Excel formula to convert ISO date to month (C2=date) and it works perfect:
=MONTH(DATE(YEAR(C2),MONTH(C2)+(WEEKDAY(C2,2)+(DAY(DATE(YEAR(C2),MONTH(C2)+1,0)))-(DAY(C2))<4),(((7-(WEEKDAY(C2,2)))+(DAY(C2)))>3)))
But when I modify it for an Access query it does not return the correct values:
Date_to_Month:MONTH(DATESERIAL(YEAR([WW_Index].[ISO_date]),MONTH([WW_Index].[ISO_date])+(WEEKDAY([WW_Index].[ISO_date],2)+(DAY(DATESERIAL(YEAR([WW_Index].[ISO_date]),MONTH([WW_Index].[ISO_date])+1,0)))-(DAY([WW_Index].[ISO_date]))<4),(((7-(WEEKDAY([WW_Index].[ISO_date],2)))+(DAY([WW_Index].[ISO_date])))>3)))
I also need to convert ISO week_year to Month. I found this formula but it does not work:
=MONTH(DATE(YEAR(C2),1,-2)-WEEKDAY(DATE(YEAR(C2),1,3))+D2*7)
Example: week 18, 2012 is the ISO week of Apr 30 through May 6, 2012. There is less that 4 April days in this week thus week 18, 2012 is in May.
Any help would be greatly appreciated.
I don't know access but you can do the first part (date to month) much more easily in excel with this formula
=MONTH(C2-WEEKDAY(C2-1)+4)
That should be easier to convert for access......
For the second part you are finding the Monday of the relevant week, hence you get the wrong month in some cases, the Thursday of the week (midpoint) should always be within the correct month so you can just add 3 to get that (-2 becomes 1), i.e.
=MONTH(DATE(YEAR(C2),1,1)-WEEKDAY(DATE(YEAR(C2),1,3))+D2*7)
I assume C2 is a date within the relevant year and D2 is the ISO week number
but probably better to have C2 containing the year, e.g. just 2013 and then you can use
=MONTH(DATE(C2,1,1)-WEEKDAY(DATE(C2,1,3))+D2*7)
Is there a way to get the week number of a date with SQL that is database independent?
For example to get the month of a date I use:
SELECT EXTRACT(MONTH FROM :DATE)
But the EXTRACT function doesn't know about weeks in SQL92.
Please pay attention to the fact that I want a solution that is database independent! Do not misinterpret this as a question regarding MS SQL Server.
There doesn't appear to be a single standard SQL function to extract the week number from a date - see here for a comparison of how different SQL dialects can extract different dateparts from date fields.
You can try this.
declare #date datetime
select #date='2013-03-15 00:00:00'
select 'Week No: '+ convert(varchar(10),datepart(wk,#date)) as weekno
Try this one :
SELECT DATENAME(yy,GETDATE())+RIGHT(DATENAME(wk,GETDATE()),2)
To understand DATENAME, please follow this link : sqltutorials.blogspot.be/2007/05/sql-datename.html and for the right, suite101.com/article/sql-functions-leftrightsubstrlengthcharindex-a209089 . There are examples to better understand ;-) It will work on MS and other sql servers normally ;-)
The only db independent solution I see is to get the number of days between today and Jan 1 of curr. year. Then divide it by 7 and round it up. There is 73 days from Jan 1 till today, which gives 10.43 as week number. The ISO week number is 11.
Correction: the number of days between last day of the current week and Jan 1 of curr. year. In this case the ISO week is 10, and 68/7 = 10 (rounded).
The best idea I found is
SELECT ROUND(((DAY(NOW())-1)/7)+1)
select (DATEPART(yyyy , CAST(GETDATE() AS datetime)) * 100 +
DATEPART(ww , CAST(GETDATE() AS datetime))) as week