How to get the total from 2 column in a week - mysql

Question

How can I get the Total Undertime for each employee per week. per month. I have a view in which it has columns undertime and overtime per day per employee. however i need to get the TotalUndertime per week.
|EmpID |DayofWeek|DatePresent|Overtime |Undertime|
|3050001|Friday |2016-04-01 | |00:01:00 |
|3050001|Monday |2016-04-04 | |01:00:00 |
|3050001|Tuesday |2016-04-05 |00:30:00 | |
|3050001|Wednesday|2016-04-06 |00:30:00 | |
|3050001|Thursday |2016-04-07 |00:05:00 | |
|3050001|Friday |2016-04-08 |00:05:00 | |
If the employee has an Undertime on Monday, the employee can pay for the Undertime on the following days from Tuesday - Friday. Or if the Employee has an Undertime on Tuesday, the employee has Wednesday - Friday to pay for the Undertime. TheTotalUndertime = "00:01:00"` in the table shown above.
I'm just a newbie when it comes to mysql queries using date and time. Should i use function or procedure?
I used this code to get it but it didn't work.
CREATE DEFINER = `root`#`localhost` PROCEDURE `getUndertime` ( IN `varDatePresent` DATE, IN `varEmpID` VARCHAR( 8 ) ) NOT DETERMINISTIC NO SQL SQL SECURITY DEFINER
BEGIN SELECT DAY( LAST_DAY( varDatePresent ) )
INTO #totaldays ;
SET #daycount =0;
WHILE(
#daycount < #totaldays
) DO SELECT Undertime
FROM view_dtr
WHERE EmpID LIKE '%varEmpID%'
AND DatePresent = varDatePresent
INTO #undertime ;
SELECT Overtime
FROM view_dtr
WHERE EmpID LIKE '%varEmpID%'
AND DATE_ADD( DatePresent, INTERVAL 1
DAY )
INTO #overtime ;
SET #totalUndertime = #undertime - #overtime ;
SET #daycount = #daycount +1;
END WHILE;
SELECT #totalUndertime ;
END ;
Any suggestion will help me very much.
Thank You in advance.

Answer 1

Wouldn't Group By do the trick?
SELECT EMPID, Week(DatePresent) as 'WeekNumber',
SEC_TO_TIME(SUM(COALESCE(undertime,0)-COALESCE(overtime,0)) * 3600) as 'TotalUndertime'
FROM table_name GROUP BY EmpID, Week(DatePresent)
Usage: https://dev.mysql.com/doc/refman/5.5/en/date-and-time-functions.html#function_week
Edit: Based on your definition of TotalUndertime. As a side note, I strongly suggest not to use LIKE when filtering your EMPID.