How to calculate the difference between times and store the result in a mySQL database (VB.NET)?

Question

I'm quite new to VB and i'm working on a project to record the details of employees clocking in and clocking out. I want to know how to make it so when the 'clock in' button is clicked the time will start recording and when the 'clock out' button is pressed the time will stop recording. Also once clock out is clicked the hours in between clock in and clock out will be recorded and stored into a mySQL database.

This information will be outputted onto a DataGrid showing the time and date of when the employee has clocked in.

Then the amount of hours will be multiplied by a pre-written hourly wage .. which is already stored inside one of the tables in my mySQL database.

Any help would be appreciated.

Answer 1

You should store the event instead of the result.

Store the clock-in time as well as a row for the clock-out time. Then you will need a procedure either on your database or in the application that will iterate over the rows and match clock-ins to clock-outs.

This approach will let the application crash/terminate and restart without losing data.

Alternatively you could put the clock-in and out in the same record (different columns), and just insert the clock-out into the first row that matched employee and null clock-out.

Answer 2

I would have the clock In button fire an event in the program that created a record for the employee ID I'm assuming you have at that time.

Then once the clock out button is clicked you would fire an event that would go out to your database and pull in the first record it found with the employee ID you are looking for, a valid clock in time and a null for the clock out time. If the program didn't find something that matched all that criteria you would have to handle that however you wanted (I would do the lookup when the employee logged in or whatever and only allow them access to the clock in button if there was no record present and only allow them to use the clock out button if there was a record found for their ID).

Once you have that record in memory you should set the clock out time and calculate the difference using the clock in time that was written to the database earlier.

I would use a stored procedure in the database to handle adding/updating/managing the record and do all the calculations and whatever else you want to do at the time of the clock in/out inside the program itself. But I think its all just preference as far as where the actual processing takes place is concerned.

The most obvious reason for this is that the program can be shut down in between clock in's and clock out's without losing anything at all. If you try to keep track of it all in memory you will lose all your clock in's once the program is shut down for whatever reason(closed manually/"End Task"ed through task manager/unhandled error).