## Number of Mondays between two dates

 Author Message TaffyLewis SSC-Addicted Group: General Forum Members Points: 427 Visits: 107 Hey, I'm looking for t-sql that can take two dates and determine how many mondays are between them? Jesper-244176 Hall of Fame Group: General Forum Members Points: 3824 Visits: 33 I think this will give the number of Mondays between the two dates (both inclusive). 20060213 can be replaced by any Monday...select (datediff(d, '20060213', @Date2) + 1)/7 - datediff(d, '20060213', @Date1)/7 TaffyLewis SSC-Addicted Group: General Forum Members Points: 427 Visits: 107 This is an interesting start, but not quite what I'm looking for. In this solution you have to know the first Monday for any calculation. I'm looking to take to dates and then calculate the number of mondays between them without having to know the first Monday in T-SQL, if possible. Jesper-244176 Hall of Fame Group: General Forum Members Points: 3824 Visits: 33 I don't quite understand what you're saying. As an example, to calculate the number of Mondays in the year 2000, do as follows:select (datediff(d, '20060213', '20001231') + 1)/7 - datediff(d, '20060213', '20000101')/7Could you give an example where my method returns something wrong? TaffyLewis SSC-Addicted Group: General Forum Members Points: 427 Visits: 107 Hey, I appreciate your feedback. I'm not saying that your solution is wrong. What I'm looking for is a formula that would be inside a stored procedure. Another stored procedure will be calling it and all this stored procedure would know would be the start date and the end date. From that, I'd like to calculate the number of Mondays between the two dates.Taffy Jesper-244176 Hall of Fame Group: General Forum Members Points: 3824 Visits: 33 Something like this? create proc countMondays( @FromDate datetime, @ToDate datetime, @NumberOfMondays int output)as select @NumberOfMondays = (datediff(d, '20060213', @ToDate) + 1)/7 - datediff(d, '20060213', @FromDate)/7godeclare @count intexec countMondays '20000101', '20001231', @count outputselect @count AMIT GUPTA-263376 SSCrazy Group: General Forum Members Points: 2412 Visits: 147 For this i have created a function in which you have to pass two date from to to dateand it will calculate the no.of mondays in the given two dates Create Function Monday(@dt1 datetime,@dt2 datetime) returns intasBeginDeclare @cnt int,@dt as datetimeset @cnt=0if @dt1 < @dt2Begin set @dt=@dt1 while @dt <= @dt2 Begin if Datepart(dw,@dt)=1 Begin set @cnt=@cnt+1 set @dt=dateadd(dd,1,@dt) End set @dt=dateadd(dd,1,@dt) EndEndif @cnt=0Begin return 0EndReturn @cntEndselect dbo.Monday('2005-01-01','2005-02-28') ok bye?? Jesper-244176 Hall of Fame Group: General Forum Members Points: 3824 Visits: 33 Note that the output of your function depends on the value of @@DATEFIRST:declare @DateFirst intselect @DateFirst = @@DATEFIRSTset datefirst 1select dbo.Monday('2006-02-13','2006-02-20') --Returns 2set datefirst 7select dbo.Monday('2006-02-13','2006-02-20') -- Returns 1 (incorrect)set datefirst @DateFirst -- Resets @@DATEFIRST to original value JeffB SSCommitted Group: General Forum Members Points: 1887 Visits: 74 This could be wrapped in either a function or stored procedure. As noted above this also depends on the value of @@DATEFIRST.--using a standard seq table SELECT TOP 9999 IDENTITY(INT,0,1) AS N INTO #Seq FROM Master.dbo.SysComments sc1, Master.dbo.SysComments sc2declare @startdate datetimedeclare @enddate datetimeselect @startdate = '13 Feb 2006', @enddate = '20 Feb 2006'select sum(case when datepart(dw, dateadd(dd, s.n, @startdate)) = 1 then 1 else 0 end)from #seq swhere s.n <= datediff(dd, @startdate, @enddate)drop table #SEQ Harley Arnett-275660 Old Hand Group: General Forum Members Points: 307 Visits: 371 Amit,Nice function - I think one small change could also speed it up - since weeks are a predictable format, when you encounter a Monday skip ahead the next 6 days - the second dateadd will then add one more day - once you find a Monday, you only need to check the Mondays....Create Function Monday(@dt1 datetime,@dt2 datetime) returns intasBeginDeclare @cnt int,@dt as datetimeset @cnt=0if @dt1 < @dt2Begin set @dt=@dt1 while @dt <= @dt2 Begin if Datepart(dw,@dt)=1 Begin set @cnt=@cnt+1 set @dt=dateadd(dd,6,@dt) End set @dt=dateadd(dd,1,@dt) EndEndif @cnt=0Begin return 0EndReturn @cntEndselect dbo.Monday('2005-01-01','2005-02-28') Regards,Harley

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