Grouping date periods (by number of days) but exclude the weekends? - sql-server

Question

I have a table with start and end dates in. My goal is to have a table that has grouped these dates into how many days the period spans. I thought I had the solution with a simple SQL statement (MS SQL Server 2005) but I want to exclude weekends.
SELECT DATEDIFF(D, StartDate, EndDate)+1 AS Days,
COUNT(ID) as Count
FROM myDateTable
GROUP BY DATEDIFF(D, StartDate, EndDate)
This gives a record set of:
Days Count
1 4
2 2
4 1
7 2
Is this possible to exclude the weekends in the SQL statement and if not can it be done using ASP and a array perhaps?

Answer 1

Well then, using Sql Server 2005, you can try something like
DECLARE #Table TABLE(
ID INT,
StartDate DATETIME,
EndDate DATETIME
)
INSERT INTO #Table (ID,StartDate,EndDate) SELECT 1, '25 Jan 2009', '31 Jan 2009'
INSERT INTO #Table (ID,StartDate,EndDate) SELECT 2, '01 Jan 2009', '07 Jan 2009'
INSERT INTO #Table (ID,StartDate,EndDate) SELECT 3, '01 Jan 2009', '14 Jan 2009'
DECLARE #MinDate DATETIME,
#MaxDate DATETIME
SELECT #MinDate = MIN(StartDate) ,
#MaxDate = MAX(EndDate)
FROM #Table
--Create a temp result set between the Min and Max dates, with all dates, and their weekday names
;WITH DayValues AS(
SELECT #MinDate DateVal,
DATENAME(dw, #MinDate) DateValName
UNION ALL
SELECT DateVal + 1,
DATENAME(dw, DateVal + 1) DateValName
FROM DayValues
WHERE DateVal + 1 <= #MaxDate
),
--select the count of days for each StartDate and EndDate pair, excluding Saturdays and Sundays
DateCounts AS(
SELECT ID,
(
SELECT COUNT(1)
FROM DayValues
WHERE DateVal BETWEEN StartDate AND EndDate
AND DateValName NOT IN ('Saturday', 'Sunday')
) DateCount
FROM #Table
)
--Now group and count
SELECT DateCount,
COUNT(ID) TotalCount
FROM DateCounts
GROUP BY DateCount
OPTION (MAXRECURSION 0)
Output
DateCount TotalCount
----------- -----------
5 2
10 1
EDIT: Brief Explenation
You need to determine the number of days between (and including) 2 dates, that are not weekends.
So using a CTE, I create a temporary result set of dates ebwteen the Min and Max dates, and their Weekday Name (eg Monday, Tuesday... Sunday).
Then, for each of your date pairs, I count the number of entries that does not correspond to Saturday and Sunday.

Answer 2

Here's an ASP function that counts days weekdays between two dates.
<%
Dim StartDate, EndDate
StartDate = CDate("1/1/2010")
EndDate = CDate("2/1/2010")
Response.Write(WeekDayCount(StartDate, EndDate))
Function WeekDayCount(StartDate, EndDate)
dim tempDate, dayCount
tempDate = StartDate
dayCount = 0
'Step forward one day, counting non-week days
While tempDate <> EndDate
'The 1 and 7 might need to be tweaked depending on the locale of your
'server. 1 = Sunday, 7 = Saturday
If DatePart("w", tempDate) <> 1 And DatePart("w", tempDate) <> 7 Then
dayCount = dayCount + 1
End If
tempDate = DateAdd("d", 1, tempDate)
Wend
WeekDayCount = dayCount
End Function
%>

Answer 3

Have a look at ##DATEFIRST,
and look a this;
SELECT DATEPART(DW,GETDATE()).
You should be able to run a query WHERE the 'DW' is not equal to the weekend numbers.