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 d

Answer 1

SELECT opened,employee,count(*)
FROM employee LEFT JOIN orders
WHERE opened < firstDate and opened > secondDate
GROUP BY opened,employee

or you can change the first condition in

WHERE opened BETWEEN firstDate and secondDate

Answer 2

Calling the result column count was a bit odd because it seems to be in fact a row number. You can do that by using ROW_NUMBER.

The other interesting part is that you also want open date and close date as separate rows. Using a simple UNION will solve that.

WITH cte 
     AS (SELECT Row_number() OVER ( PARTITION BY employee  
                                    ORDER BY order_ref) count, 
                employee, 
                opened, 
                closed 
         FROM   orders) 
SELECT employee,  opened date,  count 
FROM   cte 
UNION ALL 
SELECT employee,  closed date,  count 
FROM   cte 
ORDER  BY Date, 
          employee 

DEMO

Answer 3

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

Answer 4

My favorite way to do this counts the number of cumulative opens and the number of cumulative closes over time.

with cumopens as
    (select employee, opened as thedate,
            row_number() over (partition by employee order by opened) as cumopens,
            0 as cumcloses
     from eo
    ),
     cumcloses as
    (select employee, closed as thedate, 0 as cumopens,
            row_number() over (partition by employee order by closed ) as cumcloses
     from eo
    )
select employee, c.thedate, max(cumopens), max(cumcloses),
       max(cumopens) - max(cumcloses) as stillopened
from ((select *
       from cumopens
      ) union all
      (select *
       from cumcloses
      )
     ) c
group by employee, thedate

The only problem with this approach is that only dates where there is employee activity get reported. This works in your case.

The more general solution requires a sequence numbers to generate dates. For this, I often create one from some existing table with enough rows:

with nums as
    (select row_number() over (partition by null order by null) as seqnum
     from employees
    )
select employee, dateadd(day, opened, seqnum) as thedate, count(*)
from eo join
     nums
     on datediff(day, opened, closed) < seqnum
group by employee, dateadd(day, opened, seqnum)
order by 1, 2