Question

I’m new to SQL, right off the bat but slowly getting things figured out. I searched but couldn’t find anything that makes sense to me. Like I said, I’m new, I’m sorry. Using SQL Server 2008 R2 if that’s pertinent.

I have one table that’s structured like this

AccountNumber  StartDate                EndDate
  123456       2012-05-07 12:55:55.000  2012-05-09 09:53:55.000
  789012       2012-10-17 13:55:55.000  2012-11-02 10:53:55.000
  345678       2012-11-13 14:55:55.000  2012-12-14 11:53:55.000

I also have a workdays table that’s structured like this

Date        IsWorkday  DayOfWeek
2012-01-01     N          1
2012-01-02     N          2
2012-01-03     Y          3
2012-01-04     Y          4
2012-01-05     Y          5
2012-01-06     Y          6

Etc. through 2020-12-31

I didn’t set up the tables and can’t get them changed in any way. I tried, I won’t be allowed. I can’t even email the db admin directly. Neat.

I need select certain columns, which I can handle, but I need one column at the end that will be a count of the number of days between the StartDate and EndDate values, but only if the days in between are in the workdays table with a value of Y for IsWorkday. I hope that makes sense. If it’s simply not possible to do or a fantastically enormous hassle to get it done with the current structure, that’d be good to know too (so I can push for a better workdays/non-workdays table or something). Any help will be much appreciated and may possibly be exchanged for my firstborn.

Answer 1

Try this

SELECT X.*, X2.DayCnt 
FROM AccountTable X
INNER JOIN 
(
    SELECT a.accountnumber,a.StartDate, b.EndDate, Count(b.Date) DayCnt 
    FROM AccountTable a
    LEFT OUTER JOIN workdays w 
        ON a.StartDate >= w.date and 
        a.EndDate <= w.date and 
        IsWorkday = 'Y'
    GROUP BY a.accountnumber,a.StartDate, b.EndDate
) X2 
ON X.accountnumber = X2.accountnumber and
X.StartDate = X2.StartDate and X.EndDate = X2.EndDate