Question

I’m using a datagridview to display the records of a database. I also have a form that collects new data to be added to the database too. What I want to know is if the primary key is generated automatically or not once the data is inserted in the database using dataAdapter-DataSets.

I have a method in a class that handles all the tables for the different datagridviews. The client method looks like this.

public void AddNewClient (Client client)
        {
            try
            {
                DataRow dr = dataSet.Tables["Clients"].NewRow ();
                dr[1] = client.firstName;
                dr[2] = client.lastName;
                dr[3] = client.MI;
                dr[4] = client.address;
                dr[5] = client.city;
                dr[6] = client.state;
                dr[7] = client.zipcode;
                dr[8] = client.homePhone;
                dr[9] = client.cellPhone;
                dr[10] = client.otherPhone;
                dr[11] = client.faxNumber;
                dr[12] = client.email;
                dataSet.Tables["Clients"].Rows.Add (dr);

                adapterClients.Update (dataSet, "Clients");
            }
            catch (Exception e) { throw e; }
        } 

The dataSet.Tables[“Clients”] is bind to the DataGridViewClients. When the new record displays in the DataGridViewClients there’s no ClientID value. However, when I restart the application and the DataGridViewClients is displayed I can see how a new value to ClientID has been assigned. So I wonder is this something that is done automatically by SQL server or ….? I mean I don’t really know. 🙂

Answer 1

The ClientID is probably an identity column. That means the database automatically assigns a new number to each row. Even if you wanted to, you would not be allowed to set the value of the identity column yourself.

An identity column is often a primary key, but this is not always true. A primary key can be made up of any set of columns that uniquely identifies a row. It’s easy to see that an “auto-number” or identity column meets this requirement.

You can list all identity columns in your database with the following query:

select  t.name
,       c.name
from    sys.tables t
join    sys.columns c
on      c.object_id = t.object_id
where   c.is_identity = 1