SQL: Automatic numbering - sql

Question

I've got a question about SQL language which I couldn't find an answer for. I want SQL to automatically insert a number based off how much rows there are. Using an ASP.NET website I'm adding new rows and deleting rows. This means when I delete rows I want the table to automatically respond to that.
It is pretty hard to explain for me, so I already did some thinking ofcourse. I can fill it in using a C# code but when a row is deleted it ofcourse does not automatically change.
if (kisten < 4)
{
staple = 1;
}
else
{
if (staple1 >= 4)
{
staple = stapel2 + 1;
}
else
{
stapel = stapel2;
}
}
So what this means is that one staple contains 4 blocks. But I want if one row gets removed from the staple the first row of the second staple gets added to the first staple, so it gets value '1'.
Hope I am clear enough. If not, please don't hesitate to ask.
EDIT:
I am using SQL Server indeed. Here is a clear example of what I mean:
This is when everything is inserted using C# and as u can see it works fine.
This is when rows get deleted. As you can see the column 'Stapel' does not automatically change the number
What I want when rows get deleted
So after hours of trying I found a solution which works perfectly. Like so:
SqlCommand cmd11 = new SqlCommand("select count(kistid) from [dbo].[kist] where rij = '" + rij + "'", con);
int countrij = (Int32)cmd11.ExecuteScalar();
int procent = (4 / countrij * 100);
int hoeveel;
int hoeveel2 = (countrij % 4);
int hoeveel1;
if (hoeveel2 == 0)
{
hoeveel = (countrij / 4);
hoeveel1 = hoeveel;
for (int i = 0; i < hoeveel; i++)
{
SqlCommand sqlquery5 = new SqlCommand("UPDATE TOP (" + countrij + ") Kist SET Stapel ='" + hoeveel1 + "' WHERE Rij ='" + rij + "'");
sqlquery5.CommandType = System.Data.CommandType.Text;
sqlquery5.Connection = con;
sqlquery5.ExecuteNonQuery();
hoeveel1 = hoeveel1 - 1;
countrij = countrij - 4;
}
}
else
{
hoeveel = ((countrij - hoeveel2) / 4) + 1;
hoeveel1 = hoeveel;
for (int i = 0; i < hoeveel; i++)
{
SqlCommand sqlquery5 = new SqlCommand("UPDATE TOP (" + countrij + ") Kist SET Stapel ='" + hoeveel1 + "' WHERE Rij ='" + rij + "'");
sqlquery5.CommandType = System.Data.CommandType.Text;
sqlquery5.Connection = con;
sqlquery5.ExecuteNonQuery();
hoeveel1 = hoeveel1 - 1;
countrij = countrij - hoeveel2;
hoeveel2 = 4;
}
}

Answer 1

To automatically do something in a database when UPDATE, DELETE or INSERT command is executed for a given table you have to use CREATE TRIGGER to define a new trigger.
For more information just read about usage of triggers in your specific database server. For example for SQL Server you can read this.