HOWTO: Retrieve Identity Column After Insert Using ODBCDirect

• Microsoft Visual Basic Professional and Enterprise Editions 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. SQL Server maintains an environment variable named @@IDENTITY that stores the value of the last Identity column added and can be queried several different ways. This article demonstrates how the value of the Identity column is retrieved from the SQL Server Pubs database using ODBCDirect.

MORE INFORMATION

The following code example demonstrates two different ways to retrieve the Identity column. One calls a stored procedure, MyInsert, to insert a row, and returns the value of @@IDENTITY in an OUTPUT parameter; the other, issues a Select @@IDENTITY with an OpenRecordset after inserting a row without creating a stored procedure on the SQL server.

Step 1: Create Test Table in SQL Server

For testing purpose, table IColTest, is created in Pubs database with one Identity column and one VarChar column. To create a 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)

Step 2: Create Visual Basic Code

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

2. From the Project menu, select References, and then place a check next to Microsoft DAO 3.5 Object Library.

3. Add two CommandButtons, Command1, and Command2, to Form1.

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

   Dim wk As Workspace Dim cn As Connection

      Private Sub Command1_Click()
         'This procedure creates a stored procedure on a remote
         'data source, creates a querydef to call the stored
         'procedure, supplies values for the stored procedure's input,
         'parameters and returns the value of an Identity column.
         Dim qd As QueryDef
         Dim strSQL As String
   
         On Error Resume Next
         ' If stored procedure MyInsert exists on the server, drop it
         ' and recreate.
         strSQL = "DROP PROCEDURE MyInsert;"
         cn.Execute strSQL
   
         On Error GoTo 0
         ' Create stored procedure on the server.
         strSQL = "Create Procedure MyInsert @FieldVal Varchar(30), _
         @id Int OUTPUT AS "
         strSQL = strSQL & "Insert Into IColTest (F2) Values(@FieldVal) "
         strSQL = strSQL & "Select @id = @@Identity"
         cn.Execute strSQL
   
         Set qd = cn.CreateQueryDef("qry", "{ call MyInsert(?, ?) }")
         qd.Parameters(0).Direction = dbParamInput
         qd.Parameters(1).Direction = dbParamOutput
         qd.Parameters(0).Value = "RainBow"
         qd.Execute
   
         Debug.Print qd.Parameters(1)
         qd.Close
      End Sub
   
      Private Sub Command2_Click()
         Dim rs As Recordset
         Set rs = cn.OpenRecordset("SET NOCOUNT ON INSERT INTO _
         IColTest(F2) VALUES('Balloon')SELECT @@IDENTITY SET NOCOUNT OFF")
         Debug.Print rs(0)
         rs.Close
      End Sub
   
      Private Sub Form_Load()
         Dim strConnect As String
         Set wk = DBEngine.CreateWorkspace("ODBCDirect", "", "", dbUseODBC)
         strConnect = "ODBC;SERVER=MyServer;DRIVER={SQLServer}; _
         DATABASE=pubs;UID=sa;PWD=;"
         Set cn = wk.OpenConnection("", dbDriverNoPrompt, False, strConnect)
      End Sub
   
      Private Sub Form_Unload(Cancel As Integer)
         cn.Close
         wk.Close
      End Sub
   
   

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

6. Start the program or press the F5 key.

7. Click Command1, or Command2 to insert a row and display the value of @@IDENTITY in the debug window.

REFERENCES

For additional information, please see the following article in the Microsoft Knowledge Base:

   ARTICLE-ID: Q170147
   TITLE:      HOWTO: Retrieve Identity Column After Insert Using RDO

Keywords          : vb5all vb5howto
Technology        : kbodbc
Version           : WINDOWS:5.0
Platform          : WINDOWS
Issue type        : kbhowto