I have `Total Number of Seats` and `Available Seats`. How do I manage the two? - asp.net

Question

I struggled to come up with appropriate title for this thread.
Forgive me it isn't clearcut.
We have a table called Locations with following attributes:
locationID --Each location has 30 capacity seating per class
Capacity_Seating --this is total allowed seat per class per location.
When a user logs in, s/h is presented with a dropdownlist of locations to choose from. Whichever location the trainee chooses, is the location s/he is going to take the training at.
The Capacity seating for each location is 30.
As soon as the user logs in, s/he is taken to the Trainring page. The training displays general information about the classes, including the date and time of training, duration, the Capacity Seating and most importantly, available seats or Seats remaining.
If seats are still available, the user can click Register to register for that particular training.
Once this user is registered, the available seat changes.
For instance, if there were 15 seats prior to this trainee registering, then after registering, the available seating with now read 14 seats.
If a user chooses to cancel his or her seat after initially registering, the trainee can do so as long as it isn't within 24 hours of training date.
Here are my questions.
1, do I need to add another field called Available_Seats to the location table or to the Training table to show how many seats remain or can this be done using a query like:
Select (Capacity_Seating - each time trainee registers)?? Not sure how to handle this.
2, We would like to use register to substract a number from Capacity_Seating and Cancel to put back a number to Capacity_Seating.
Your thoughts and assistance are greatly appreciated.
<ItemTemplate>
<asp:LinkButton ID="Btncalc" runat="server" Text="Register" tooltip="Click to calculate" onclick="calc" />
</ItemTemplate>
</asp:TemplateField>
</ItemTemplate>
Sub calc(ByVal sender As Object, ByVal e As System.EventArgs)
Dim objConnection As SqlConnection
Dim username = Session.Item("Username").ToString
' Dim strSQL As String
objConnection = New SqlConnection(ConfigurationManager.ConnectionStrings("DBConnectionString").ConnectionString)
objConnection.Open()
strSQL = "update TrainingTable set employeeId='" & username
strSQL += "', AvailableSeats= AvailableSeats-1"
strSQL += " where location = '" & ddlLocation.SelectedValue.ToString & "'"
'Response.Write(strSQL)
'Response.End()
Dim cmdcommand As New SqlCommand(strSQL, objConnection)
cmdcommand.ExecuteNonQuery()
cmdcommand = Nothing
objConnection.Close()
objConnection = Nothing
End Sub
By the way, markup is on gridview.

Answer 1

For your first question how you would like to proceed mostly comes down to what you would like to do. Having another field for the available seats in a table or finding the remaining seats using a query are both viable options. The benefits or pitfalls of either are really negligible given the basic structure of your system. Seeing as you would use a specific query to find this piece of information constantly it would be better practice and sense to add this value in as a new field in the table. This will eliminate the need for a specific query and make this data more public to other systems and queries.
For your second question I'm not quite sure I follow it but I'll try to give you my best opinion. It seems you want to alter the total capacity field from each table based on registrations and cancellations which I would disagree with. The capacity value shouldn't be modified if the actually total capacity of location does not change. So rather than changing the total capacity through cancels or registrations I would change that new available seats field. This leaves no chance for confusion when viewing the capacity of the location and will easily allow you to find the available spaces for registration.

Answer 2

This is a simple module:
It gives you a choice of a particular course, with two venues and an option of reg or adv course at each venue (this doesn't affect the seating)
I have NOT included the SQL OR server side scripts, at this stage.. this algorithm should help.
You don't need to add another column to your table, just update the fields as the program is implemented, and you can delete a row, if it is cancelled. I haven't included code for that.. (it's too long!!! hahaha)
(NB this doesn't error check for datatype - it's a simple format to get an idea)
Module Module1
Sub main()
Dim Seat As Object
Dim Course As Object
Dim Person1 As Integer
Dim Venue1 As Integer
Dim Venue2 As Integer
Dim regular As Integer
Dim Advanced As Integer
Dim x As String
Do
Person1 = Person1 + 1
If Venue1 = 30 Then
Console.WriteLine("Venue1 is full")
End If
If Venue2 = 30 Then
Console.WriteLine("Venue2 is full")
End If
Console.WriteLine("enter 1 for Venue1, 2 for Venue2")
Seat = Console.ReadLine
If Seat = 1 Then
Venue1 = Venue1 + 1
Else
Venue2 = Venue2 + 1
End If
Console.WriteLine("Regular course = 1, Advanced course = 2")
Course = Console.ReadLine
If Course = 1 Then
regular = regular + 1
Else
Advanced = Advanced + 1
End If
Console.WriteLine("Press enter to continue, r for reports or x to quit")
x = Console.ReadLine
If x = "r" Then
Console.WriteLine("total Persons= " & Person1 & vbCrLf & "total Venue1= " & Venue1 & vbCrLf & "total Venue2=" & Venue2 & vbCrLf & "Course: regular " & regular & vbCrLf & "Advanced " & Advanced)
ElseIf x = "x" Then
Exit Do
Else
End If
Loop Until Person1 = 60
If Person1 = 60 Then
Console.WriteLine("Course is full.")
End If
End Sub
End Module
Please let me know if you need any more help or clarity.