Question

my sql server table named timesheet has 4 columns

employee_id int
task_start_date datetime
task_end_date datetime
hours_worked int

I need to derive week start date and week end date and total hours the employee has worked in that week. My resulting dataset should have 4 columns –
Week_Start_Date Week_End_Date Employee_Id Total_Hours_Charged

In other words, i need to get total hours charged by each employee for all the weeks from that table. Could anyone please help me write a query for that?

Answer 1

SQL Server 2005 and above

Assumptions:

1. Task start and end date values are always same.
2. Week start and end dates are calculated based on the task_start_date.

You can use the DATEPART function to find the day of the week for a given date and then use DATEADD function to provide the output from DATEPART as input to calculate the first and last days of the week.

Click here to view the demo in SQL Fiddle.

Script:

The script calculates the week totals hours assuming that week begins on Sunday and ends on Saturday.

CREATE TABLE timesheet
(
        employee_id     int
  ,     task_start_date datetime
  ,     task_end_date   datetime
  ,     hours_worked    int
);

INSERT INTO timesheet
    (employee_id, task_start_date, task_end_date, hours_worked) 
    VALUES
      (1, '20120331', '20120331', 6),
      (1, '20120401', '20120401', 3),
      (1, '20120403', '20120403', 8),
      (1, '20120409', '20120409', 5),
      (1, '20120412', '20120412', 4),
      (2, '20120402', '20120402', 7),
      (2, '20120403', '20120403', 6),
      (3, '20120409', '20120409', 4),
      (1, '20120412', '20120412', 8);

;WITH empworkhours AS
(
    SELECT  DATEADD(DAY
                ,   -(DATEPART(dw, task_start_date) -1)
                ,   task_start_date) AS week_start
        ,   DATEADD(DAY
                ,   7 - (DATEPART(dw, task_start_date))
                ,   task_start_date) AS week_end
        ,   employee_id
        ,   hours_worked
    FROM    timesheet
)
SELECT      week_start
        ,   week_end
        ,   employee_id
        ,   SUM(hours_worked) total_hrs_per_week
FROM        empworkhours
GROUP BY    week_start
        ,   week_end
        ,   employee_id;

Output:

WEEK_START      WEEK_END        EMPLOYEE_ID TOTAL_HRS_PER_WEEK
--------------  --------------  ----------- -----------------
March, 25 2012  March, 31 2012       1               6
April, 01 2012  April, 07 2012       1              11
April, 01 2012  April, 07 2012       2              13
April, 08 2012  April, 14 2012       1              17
April, 08 2012  April, 14 2012       3               4