Check Each Date In Date Range - sql-server-2008

Question

In SQL Server 2008 I have a startdate and an enddate being passed to my procedure. I need to check each date in the range to see if it exists in my validworkday table. I have no clue where to begin on this, but this is how start/end day are set-up
Declare #startdate date, #enddate date
Set #startdate = '01/01/2015'
Set #enddate = '04/16/2015'
Now how can I iterate each date in this span to see if validworkday = true for it? The check I would need to run is like so (checking each date)
Select isvalidworkday
from validworkdays
where date = '01/01/2015'
Select isvalidworkday
from validworkdays
where date = '01/02/2015'

Answer 1

This is syntax that I found from #Incidently years ago (I don't remember where that original post is, but hopefully this will be enough to give the credit), that I still use today. All I did was slightly tweak his syntax to insert the data into a temp table and add a cursor to iterate each individual date.
DECLARE #DateFrom smalldatetime, #DateTo smalldatetime, #firstdate date;
SET #DateFrom='20000101';
SET #DateTo='20081231';
-------------------------------
WITH T(date)
AS
(
SELECT #DateFrom
UNION ALL
SELECT DateAdd(day,1,T.date)
FROM T
WHERE T.date < #DateTo
)
SELECT date
INTO #AllDates
FROM T OPTION (MAXRECURSION 32767);
Declare c1 Cursor For
Select date
FROM #AllDates
Open c1
Fetch Next From c1 Into #firstdate
While ##FETCH_STATUS = 0
Begin
--Do whatever processing you need here
Fetch Next From c1 Into #firstdate
End
Close c1
Deallocate c1

Answer 2

Code should only live in one place and not be rewritten. Create functions (once) like GetAllIntsBetween(), GetAllMonths(), GetAllDates(), etc. Then used them like:
DECLARE #startdate date = '01/01/2015', #enddate date = '04/16/2015'
SELECT allDates.TheDate,
isnull(v.isvalidworkday, false) AS isvalidworkday
FROM dbo.GetAllDates(#startdate, #enddate) AS allDates
LEFT JOIN validworkdays AS v
ON allDates.TheDate = v.MyDate
The GetAllDates() would be:
CREATE FUNCTION dbo.GetAllDates(#Start DATETIME, #End DATETIME)
RETURNS
#AllDates TABLE
(
TheDate DATETIME
)
AS
BEGIN
IF #Start > #End
BEGIN
DECLARE #Temp DATETIME
SET #Temp = #Start
SET #Start = #End
SET #End = #Temp
END
WHILE #Start <= #End
BEGIN
INSERT INTO #AllDates
VALUES(#Start)
SET #Start = DATEADD(DAY, 1, #Start)
END
RETURN
END
(note: can change DATETIME to DATE)