HOWTO: Retrieve Identity Column After Insert Using RDO

• Microsoft Visual Basic Enterprise Edition for Windows, version 5.0

SUMMARY

SQL Server Identity columns automatically increment their value when a new record is added to the table, which makes them very useful for a unique primary key. When using RDO, you may want to know what the new value of the Identity column is after inserting a new record with the RDO Addnew/Update methods, or with a SQL INSERT statement.

SQL Server maintains an environment variable named @@IDENTITY that stores the value of the last Identity column added. This environment variable can be queried several different ways from RDO.

MORE INFORMATION

The following two code examples demonstrate how the value of the Identity column is retrieved from the SQL Server Pubs database using RDO, after a new record is inserted. For testing purpose, a temporary table, IColTest, is created in Pubs database with one Identity column and one VarChar column.

To create a temporary table and index in SQL Server, select Pubs database, then place the following Create Table T-SQL in the SQL window of ISQL/W and execute it.

   Create Table IColTest
           (Id_Col int Identity, F2 VarChar(30) Null)
   Create Unique Index IIndex on IColTest(Id_Col)

Example One

This example uses a stored procedure to insert a row by taking parameters passed from RDO, and then returns the value of @@IDENTITY in a OUTPUT parameter.

Task One: Create the Stored Procedure

To create this stored procedure, place the following Create Procedure T-SQL in the SQL window of ISQL/W and execute it:

   Create Procedure MyInsert
       @FieldVal Varchar(30), @id Int OUTPUT AS
       Insert Into IColTest (F2) Values(@FieldVal)
       Select @id = @@Identity

1. Start a new project in Visual Basic and choose "Standard EXE". Form1 is created by default.

2. Add a CommandButton to Form1, Command1 by default.

3. Paste the following code into the code window of Form1:

         Private Sub Command1_Click()
            Dim cn As New rdoConnection
            Dim qy As New rdoQuery
            Dim strConnect As String
   
            strConnect = "Driver={SQL Server}; Server=MyServer; _
                          Database=Pubs; Uid=sa; Pwd="
            With cn
              .Connect = strConnect
              .LoginTimeout = 5
              .EstablishConnection rdDriverNoPrompt, True
            End With
            With qy
              Set .ActiveConnection = cn
              .SQL = "{Call MyInsert(?, ?)}"
            End With
            qy(0).Direction = rdParamInput
            qy(1).Direction = rdParamOutput
            qy(0) = "RainBow"
            qy.Execute
   
            Debug.Print qy(1)
         End Sub
   
      In Visual Basic 5.0, you can also use the User Connection Designer (CQD)
      to create rdoQuery objects in your project. The CQD takes your SQL query
      and permits you to specify the data types for each parameter. It then
      inserts appropriate code in your application to expose these procedures
      very much like methods off the rdoQuery object.
   
   

4. Note that you must change your SERVER, UID, and PWD parameters in the connect string.

5. Start the program or press the F5 key.

6. Click Command1 button to insert a row and display value of @@IDENTITY in the debug window.

Example Two

You can also do a Select @@IDENTITY with an OpenResultset after inserting a row without creating a stored procedure on the SQL server.

1. Add another CommandButton to Form1, Command2 by default.

2. Paste the following code into the code window of Form1:

         Private Sub Command2_Click()
             Dim cn As New rdoConnection
             Dim rs As rdoResultset
             Dim strConnect as string
   
             strConnect = "Driver={SQL Server}; Server=MyServer; _
                          Database=Pubs; Uid=sa; Pwd="
             With cn
                .Connect = strConnect
                .LoginTimeout = 5
                .EstablishConnection rdDriverNoPrompt, True
             End With
   
             Set rs = cn.OpenResultset _
         ("SET NOCOUNT ON _
                INSERT INTO IColTest(F2) VALUES('Balloon') _
                SELECT @@IDENTITY _
                SET NOCOUNT OFF")
              Debug.Print rs(0)
              rs.Close
              cn.Close
          End Sub
   
   

3. Note that you must change your SERVER, UID, and PWD parameters in the Connect method.

4. Start the program or press the F5 key.

5. Click the Command2 button to insert a row to table IColTest and display value of @@IDENTITY in the debug window.

REFERENCES

For additional information of User Connection Designer, please see the following article in the Microsoft Knowledge Base:

   ARTICLE-ID: Q166281
   TITLE: HOWTO: Create and Implement a UserConnection

 (c) Microsoft Corporation 1997, All Rights Reserved.

Keywords          : vb5all kbhowto
Version           : 5.0
Platform          : WINDOWS