MSSQL select count where condition is met across a date range - sql

Question

I have a table containing date, employeeID(int) , and ShiftWorked (can be night/day/weekend or evening) . There is a row for each employee and date combination
I would like to construct a query that gives me a count of how many people have worked a night shift in the week before and after each date in the roster period.
--------------------------------------------------------------------------
Date (yyyy-MM-dd) | CountOfNightshifts(for 1 week either side of date)
--------------------------------------------------------------------------
2012-1-1 | 8
2012-1-2 | 12
2012-1-3 | 11
2012-1-4 | 6
etc | etc
I hope this is clear. I have spent days trying to get this to work but I am not getting anywhere.
For example:
SELECT COUNT(id), [date]
FROM ROSTER
WHERE Shift = night AND [date] BETWEEN DATEADD(D,-7,[date]) AND DATEADD(d,7,[date])
GROUP by [date]
group by [date]
This will give me a list of dates and a count of nights on that particular day - not all night shifts in the 7 days before and after the date.

Answer 1

The following query will return two columns: the reference (roster) date and the number of (distinct) people that have worked on the night sift seven days before to seven days after the reference date.
SELECT tmain.date,
(
SELECT COUNT(DISTINCT taux.employeeId)
FROM roster taux
WHERE taux.shiftWorked = 'night'
AND taux.date >= DATEADD(DAY, -7, tmain.date)
AND taux.date <= DATEADD(DAY, 7, tmain.date)
) AS [number_of_distinct_people_with_night_shift]
FROM roster tmain
ORDER BY tmain.date;
Note 1: Usually I prefer joins over sub-queries, but I guess this solution is easier to read.
Note 2: I am assuming the time component of date values are irrelevant and all dates have the same time (i.e. '00:00:00.00'); if it is not the case, there are more adjustments to be done on the date comparison.

Answer 2

how about this?
SELECT
[date]
,count(*)
FROM
Shifts as s
WHERE
s.Date > DATEADD(day,-7,GETDATE())
AND ShiftWorked = 'Night'
GROUP BY
date
http://sqlfiddle.com/#!3/e88cc/1
a bit more data:
http://sqlfiddle.com/#!3/b7793/2
If you are only interested in a specific date then you could use:
DECLARE #target datetime
SET #target = GETDATE()
SELECT
count(*) as NightShifts
FROM
Shifts as s
WHERE
ShiftWorked = 'Night'
AND s.Date > DATEADD(day,-7,#target)
AND s.Date < DATEADD(day,7,#target)
http://sqlfiddle.com/#!3/b7793/20
but if you have another table that actually has the periods in it (e.g. billing or payroll dates):
DECLARE #target datetime
SET #target = GETDATE()
SELECT
p.periodDate
,count(*)
FROM
Shifts as s
INNER JOIN periods as p
ON s.date > dateadd(day,-7,p.periodDate)
AND s.date < dateadd(day,7,p.periodDate)
WHERE
ShiftWorked = 'Night'
GROUP BY p.periodDate
http://sqlfiddle.com/#!3/fc54d/2
OR to get ) when no night shift was worked:
SELECT
p.periodDate
,ISNULL(t.num,0) as nightShifts
FROM
periods as p
LEFT OUTER JOIN (
SELECT
p.periodDate
,count(*) as num
FROM
Shifts as s
INNER JOIN periods as P
ON s.date > dateadd(day,-7,p.periodDate)
AND s.date < dateadd(day,7,p.periodDate)
WHERE
ShiftWorked = 'Night'
GROUP BY p.periodDate
) as t
ON p.periodDate = t.periodDate
http://sqlfiddle.com/#!3/fc54d/11

Answer 3

You can pull it off by joining the ROSTER table to itself, thereby creating several result rows per employee and day. Otherwise your GROUP BY clause will group the resulting rows from the period you are after into the dates of the original table.
SELECT
r.[date],
COUNT(period.id)
FROM ROSTER r
JOIN ROSTER period
ON period.employeeID=r.employeeID
AND period.shift = night
AND r.[date] BETWEEN DATEADD(d,-7,period.[date]) and DATEADD(d,7,period.[date])
WHERE
r.shift = night
GROUP BY r.[date]