Insert primary key to other tables using VB.NET - sql

Question

I'm using SQL Server as my DBMS and I have 2 tables namely Person and Voter.
Person has these columns:
PersonId (int, primary key auto-increment int_identity),
FirstName (nvarchar(50))
LastName (nvarchar(50))
Voter has these columns:
VoterPersonId (int, foreign key)
VoterPlace (nvarchar(50))
These 2 tables are related. For 1 person there can only be 1 voter place. So you may call it a one is to one relationship. I created 2 tables because there are also people who aren't voters that I must include in my database and I don't want to create null values so I made a separate table which is the 'voter' table. Basically, I wanted to know the number registered voters and non-voters in our city. Now, I have created a 'save' button in VB.NET and used the following code to insert information into my tables:
Dim sql As New SQLControl
Private Sub cmdSave_Click_1(ByVal sender As System.Object, ByVal e As System.EventArgs) Handles cmdSave.Click
sql.con.Open()
Using cmdPerson As New SqlClient.SqlCommand("INSERT INTO Person(FirstName, LastName) VALUES('" & txtFirstName.Text & "', '" & txtLastName.Text & "')", sql.con)
cmdPerson.ExecuteNonQuery()
End Using
Using cmdVoter As New SqlClient.SqlCommand("INSERT INTO Voter(VoterPlace) VALUES('" & txtVoterPlace.Text & "')", sql.con)
cmdVoter.ExecuteNonQuery()
End Using
sql.con.Close()
End Sub
Now, my problem is I don't know how to transfer the value of 'PersonId' primary key which is auto-increment in_identity into 'VoterPersonId' the moment I click on the 'save' button. Is it possible? Can you please help me on this matter? I would really appreciate it.

Answer 1

You can execute both queries in a single stored procedure
CREATE PROCEDURE InsertPerson
#firstname varchar(50),
#lastname varchar(50),
#voterPlace varchar(50)
AS
declare #newid int
INSERT INTO Person(Firstname, Lastname) VALUES (#firstname, #lastname)
SELECT #newid = SCOPE_IDENTITY()
INSERT INTO Voter(VoterPersonId, VoterPlace) VALUES ( #newid, #voterPlace)

Answer 2

You can use a stored procedure but you certainly don't have to. The principle is still the same though. You execute the insert to the parent table and then use the SCOPE_IDENTITY function to get the auto-generated ID. You would then use an output parameter to get that value back into your app so that you can include it in the next insert to the child table, e.g.
Using connection As New SqlConnection("connection string here"),
parentCommand As New SqlCommand("INSERT INTO Parent (ParentName) VALUES (#ParentName); SET #ParentId = SCOPE_IDENTITY();", connection),
childCommand As New SqlCommand("INSERT INTO Child (ParentId, ChildName) VALUES (#ParentId, #ChildName)", connection)
With parentCommand.Parameters
.AddWithValue("#ParentName", parentName)
.Add("#ParentId", SqlDbType.Int).Direction = ParameterDirection.Output
End With
connection.Open()
Dim transaction = connection.BeginTransaction()
Try
parentCommand.ExecuteNonQuery()
With childCommand.Parameters
.AddWithValue("#ParentId", parentCommand.Parameters("#ParentId").Value)
.AddWithValue("#ChildName", childName)
End With
childCommand.ExecuteNonQuery()
transaction.Commit()
Catch
transaction.Rollback()
End Try
End Using