I have s table that lists absences(holidays) of all employees, and what we would like to find out is who is away today, and the date that they will return.
Unfortunately, absences aren't given IDs, so you can't just retrieve the max date from an absence ID if one of those dates is today.
However, absences are given an incrementing ID per day as they are inputt, so I need a query that will find the employeeID if there is an entry with today's date, then increment the AbsenceID column to find the max date on that absence.
Table Example (assuming today's date is 11/11/2014, UK format):
AbsenceID EmployeeID AbsenceDate
100 10 11/11/2014
101 10 12/11/2014
102 10 13/11/2014
103 10 14/11/2014
104 10 15/11/2014
107 21 11/11/2014
108 21 12/11/2014
120 05 11/11/2014
130 15 20/11/2014
140 10 01/03/2015
141 10 02/03/2015
142 10 03/03/2015
143 10 04/03/2015
So, from the above, we'd want the return dates to be:
EmployeeID ReturnDate
10 15/11/2014
21 12/11/2014
05 11/11/2014
Edit: note that the 140-143 range couldn't be included in the results as they appears in the future, and none of the date range of the absence are today.
Presumably I need an iterative sub-function running on each entry with today's date where the employeeID matches.
So based on what I believe you're asking, you want to return a list of the people that are off today and when they are expected back based on the holidays that you have recorded in the system, which should only work only on consecutive days.
Schema Setup:
CREATE TABLE EmployeeAbsence
([AbsenceID] int, [EmployeeID] int, [AbsenceDate] DATETIME)
;
INSERT INTO EmployeeAbsence
([AbsenceID], [EmployeeID], [AbsenceDate])
VALUES
(100, 10, '2014-11-11'),
(101, 10, '2014-11-12'),
(102, 10, '2014-11-13'),
(103, 10, '2014-11-14'),
(104, 10, '2014-11-15'),
(107, 21, '2014-11-11'),
(108, 21, '2014-11-12'),
(120, 05, '2014-11-11'),
(130, 15, '2014-11-20')
;
Recursive CTE to generate the output:
;WITH cte AS (
SELECT EmployeeID, AbsenceDate
FROM dbo.EmployeeAbsence
WHERE AbsenceDate = CAST(GETDATE() AS DATE)
UNION ALL
SELECT e.EmployeeID, e.AbsenceDate
FROM cte
INNER JOIN dbo.EmployeeAbsence e ON e.EmployeeID = cte.EmployeeID
AND e.AbsenceDate = DATEADD(d,1,cte.AbsenceDate)
)
SELECT cte.EmployeeID, MAX(cte.AbsenceDate)
FROM cte
GROUP BY cte.EmployeeID
| EMPLOYEEID | Return Date |
|------------|---------------------------------|
| 5 | November, 11 2014 00:00:00+0000 |
| 10 | November, 15 2014 00:00:00+0000 |
| 21 | November, 12 2014 00:00:00+0000 |
Explanation:
The first SELECT in the CTE gets employees that are off today with this filter:
WHERE AbsenceDate = CAST(GETDATE() AS DATE)
This result set is then UNIONED back to the EmployeeAbsence table with a join that matches EmployeeID as well as the AbsenceDate + 1 day to find the consecutive days recursively using:
-- add a day to the cte.AbsenceDate from the first SELECT
e.AbsenceDate = DATEADD(d,1,cte.AbsenceDate)
The final SELECT simply groups the cte results by employee with the MAX AbsenceDate that has been calculated per employee.
SELECT cte.EmployeeID, MAX(cte.AbsenceDate)
FROM cte
GROUP BY cte.EmployeeID
Excluding Weekends:
I've done a quick test based on your comment and the below modification to the INNER JOIN within the CTE should exclude weekends when adding the extra days if it detects that adding a day will result in a Saturday:
INNER JOIN dbo.EmployeeAbsence e ON e.EmployeeID = cte.EmployeeID
AND e.AbsenceDate = CASE WHEN datepart(dw,DATEADD(d,1,cte.AbsenceDate)) = 7
THEN DATEADD(d,3,cte.AbsenceDate)
ELSE DATEADD(d,1,cte.AbsenceDate) END
So when you add a day: datepart(dw,DATEADD(d,1,cte.AbsenceDate)) = 7, if it results in Saturday (7), then you add 3 days instead of 1 to get Monday: DATEADD(d,3,cte.AbsenceDate).