Find consecutive working dates for each employee - sql

Question

In SQL 2000 I have a table that contains the following:
ID Date WorkingTime EmployeeID
For August, this table would contain 200 employees with dates of 8/1 - 8/31. I need to find out what is the MIN date of the first 5 consecutive days of working time for each employee starting at the day passed in and going backward.
For Example:
If employee 123 looked as follows and 8/10/2013 was passed in:
ID Date WorkingTime EmployeeID
1 8/1 1 123
2 8/2 0 123
3 8/3 0 123
4 8/4 1 123
5 8/5 1 123
6 8/6 1 123
7 8/7 1 123
8 8/8 1 123
9 8/9 0 123
10 8/10 1 123
The result would be 8/4. This needs to be done all at once for all of the employees in the table, so they would all have different min dates, all starting on 8/10 since that was the date that was passed into the query. This table is very large in real life and contins many dates and employees, not just in Auguest. I thought about using a cursor to go through all of this but I think that would be really slow. I was also thinking of adding all of the working times to a temp table and doing a datediff on them to find the consecutive 5 with a datediff of 1, but I wasn't quite sure how to execute that. Is there a better way I am not thinking of?

Answer 1

DECLARE #MyTable TABLE
(
ID INT IDENTITY PRIMARY KEY,
[Date] SMALLDATETIME NOT NULL,
WorkingTime INT NOT NULL,
EmployeeID INT NOT NULL
);
INSERT #MyTable ([Date], WorkingTime, EmployeeID)
-- First employee
SELECT '20130801', 1, 123 UNION ALL
SELECT '20130802', 0, 123 UNION ALL
SELECT '20130803', 0, 123 UNION ALL
SELECT '20130804', 1, 123 UNION ALL
SELECT '20130805', 1, 123 UNION ALL
SELECT '20130806', 1, 123 UNION ALL
SELECT '20130807', 1, 123 UNION ALL
SELECT '20130808', 1, 123 UNION ALL
SELECT '20130809', 0, 123 UNION ALL
SELECT '20130810', 1, 123 UNION ALL
-- Second employee
SELECT '20130801', 1, 126 UNION ALL
SELECT '20130802', 1, 126 UNION ALL
SELECT '20130803', 1, 126 UNION ALL
SELECT '20130804', 1, 126 UNION ALL
SELECT '20130805', 1, 126 UNION ALL
SELECT '20130806', 0, 126 UNION ALL
-- Third employee
SELECT '20130801', 0, 127 UNION ALL
SELECT '20130802', 0, 127 UNION ALL
SELECT '20130803', 1, 127 UNION ALL
SELECT '20130804', 1, 127 UNION ALL
SELECT '20130805', 0, 127 UNION ALL
SELECT '20130806', 0, 127;
--
DECLARE #Results TABLE
(
EmployeeID INT NOT NULL,
DaysDiff INT NOT NULL,
PRIMARY KEY(EmployeeID, DaysDiff), -- This is a "clustered index"/index organized table
RowNum INT IDENTITY NOT NULL,
[Date] SMALLDATETIME NOT NULL
);
INSERT #Results (EmployeeID, DaysDiff, [Date])
SELECT x.EmployeeID,
DATEDIFF(DAY, 0, x.[Date]) AS DaysDiff,
x.[Date]
FROM #MyTable x
WHERE x.WorkingTime = 1
/*
This ORDER BY clause and the clustered index (PRIMARY KEY(EmployeeID, DaysDiff))
should give a hint to SQL Server so that
RowNum IDENTITY values will be generated in this order: EmployeeID, DaysDiff
Note #1: There is not 100% guarantee that insert order will be the same as
ORDER BY x.EmployeeID, DaysDiff
and
clustered index key (EmployeeID, DaysDiff)
Note #2: This INSERT INTO table with identity column simulates the ROW_NUMBER function
which is available starting with SQL2005.
*/
ORDER BY x.EmployeeID, DaysDiff
OPTION (MAXDOP 1); -- It minimizes the risk of messing up the order of RowNum
SELECT y.EmployeeID, MAX(y.GroupStartDate) AS FirstGroupStartDate
FROM
(
SELECT x.EmployeeID, x.GroupID,
MIN(x.[Date]) AS GroupStartDate, MAX(x.[Date]) AS GroupEndDate,
DATEDIFF(DAY, MIN(x.[Date]), MAX(x.[Date]))+1 AS ContinuousDays
FROM
(
SELECT *, r.DaysDiff - r.RowNum AS GroupID
FROM #Results r
) x
GROUP BY x.EmployeeID, x.GroupID
) y
WHERE y.ContinuousDays > 4
GROUP BY y.EmployeeID;

Answer 2

Below query will give good start for what you want to achieve, modify the schema based on your tables.
SQL fiddle demo
#DateToPull - Date for which you want to pull data for.
#TimeSheet is your original table
#SubsetTimeSheet - table with subset of records from #TimeSheet table. Populated with records from first of the month till passed date.
Note: This query can be written more efficiently with newer version of SQL Server.
declare #DateToPull datetime
select #DateToPull = '08/10/2013'
if object_id('tempdb..#TimeSheet') is not null
drop table #TimeSheet
create table #TimeSheet
(
ID int identity(1, 1),
EmployeeID int,
[WorkDate] datetime,
WorkingTime bit
)
insert into #TimeSheet(EmployeeID, [WorkDate], WorkingTime)
select 123 , '08/01/2013', 0
union all
select 123 , '08/02/2013', 1
union all
select 123 , '08/03/2013', 0
union all
select 123 , '08/04/2013', 1
union all
select 123 , '08/05/2013', 1
union all
select 123 , '08/06/2013', 1
union all
select 123 , '08/07/2013', 1
union all
select 123 , '08/08/2013', 1
union all
select 123 , '08/09/2013', 0
union all
select 123 , '08/10/2013', 1
union all
select 123 , '08/11/2013', 1
union all
select 123 , '08/12/2013', 1
union all
select 123 , '08/13/2013', 1
union all
select 123 , '08/14/2013', 1
union all
select 123 , '08/15/2013', 0
union all
select 123 , '08/16/2013', 1
union all
select 123 , '08/17/2013', 1
union all
select 123 , '08/18/2013', 1
union all
select 123 , '08/19/2013', 1
union all
select 123 , '08/20/2013', 1
if object_id('tempdb..#SubsetTimeSheet') is not null
drop table #SubsetTimeSheet
create table #SubsetTimeSheet
(
EmployeeID int,
[WorkDate] datetime,
WorkingTime bit
)
insert into #SubsetTimeSheet(EmployeeID, [WorkDate], WorkingTime)
select EmployeeID, [WorkDate], WorkingTime
from #TimeSheet
where
datediff(dd, [WorkDate], #DateToPull) >= 0
and datediff(dd, DATEADD(dd, -(DAY(#DateToPull)-1), #DateToPull), [WorkDate]) >= 0
and WorkingTime = 1
order by
EmployeeID,
[WorkDate] desc
select A.EmployeeID, max(E.WorkDate) WorkDate
from
#SubsetTimeSheet A
inner join #SubsetTimeSheet B on datediff(dd, A.[WorkDate] - 1, B.WorkDate) = 0 and A.EmployeeID = B.EmployeeID
inner join #SubsetTimeSheet C on datediff(dd, A.[WorkDate] - 2, C.WorkDate) = 0 and A.EmployeeID = C.EmployeeID
inner join #SubsetTimeSheet D on datediff(dd, A.[WorkDate] - 3, D.WorkDate) = 0 and A.EmployeeID = D.EmployeeID
inner join #SubsetTimeSheet E on datediff(dd, A.[WorkDate] - 4, E.WorkDate) = 0 and A.EmployeeID = E.EmployeeID
group by
A.EmployeeID