sql server - SQL Count Of Open Orders Each Day Between Two Dates

Question

I've tried searching but it's likely I'm using the wrong keywords as I can't find an answer.

I'm trying to find the number of orders that are open between two dates and by employee. I have one table that shows a list of employees, another that shows a list of orders that contains an open and close date and also a dates table if that helps.

The employee and order tables joined will return something like:

employee    order ref   opened          closed
a           123         01/01/2012      04/01/2012
b           124         02/01/2012      03/01/2012
a           125         02/01/2012      03/01/2012

And I need to transform this data into:

Date            employee    Count
01/01/2012      a           1
02/01/2012      a           2
02/01/2012      b           1
03/01/2012      a           2
03/01/2012      b           1
04/01/2012      a           1

I'm pulling the data from SQL server.

Any ideas?

Thanks

Nick

Answer 1

Join Dates to the result of the join between Employees and Orders, then group by dates and employees to obtain the counts, something like this:

SELECT
  d.Date,
  o.Employee,
  COUNT(*) AS count
FROM Employees e
  INNER JOIN Orders o ON e.ID = o.Employee
  INNER JOIN Dates d ON d.Date BETWEEN o.Opened AND o.Closed
GROUP BY
  d.Date,
  o.Employee