HOWTO: Get Return Parameters from a Stored Procedure with DAO

• Microsoft Visual Basic Professional and Enterprise Editions for Windows, versions 4.0, 5.0

SUMMARY

Although RDO has the capability to execute stored procedures that return parameters, DAO does not. It is possible to run these stored procedures with a little bit of creative SQL.

NOTE: The SQL code used is SQL Server's Transact SQL. Other servers may require slightly different syntax but the concept is the same.

MORE INFORMATION

RDO gives the programmer direct access to input and output parameters through the rdoParameters collection of the PreparedStatement object. DAO has no equivalent functionality, but SQL does. The following Visual Basic code connects to a SQL Server, creates a stored procedure that has a return parameter, one input parameter, one input/output parameter and one output parameter, runs the stored procedure, and retrieves the output parameter values:

1. Start a new Project. Form1 is created by default.

2. Under the Tools - References menu, select the proper DAO reference.

3. Add a Command Button to the form.

4. In the Command1_Click() event, add the following code:

       Private Sub Command1_Click()
   

          Dim db As Database
          Dim rs As Recordset
          Dim strConnect As String
          Dim strSQL As String
          Dim strResult As String
   

          'Set connect string.
          strConnect = "ODBC;DSN=DSN_SP_TEST;"
   

          'Open the database
          Set db = DBEngine.Workspaces(0).OpenDatabase("", False, False, _
                                                       strConnect)
   
          'Check to see if sp exists and delete it if it does.
          strSQL = "if exists "
          strSQL = strSQL & "(SELECT * from sysobjects "
          strSQL = strSQL & "WHERE id = object_id('dbo.sp_ReturnParams') "
          strSQL = strSQL & "AND sysstat & 0xf = 4) "
          strSQL = strSQL & "DROP PROCEDURE dbo.sp_ReturnParams"
          MsgBox strSQL
          db.Execute strSQL, dbSQLPassThrough
   
          'Create the stored procedure. It really does not do much.
          'It simply sets the variables and returns
          strSQL = "/****** Object:  Stored Procedure dbo.sp_ReturnParams */"
          strSQL = strSQL & vbCrLf & "CREATE PROCEDURE dbo.sp_ReturnParams"
          strSQL = strSQL & vbCrLf & "/* Declare Parameters */"
          strSQL = strSQL & vbCrLf & "  @intInput       int = Null,  "
          strSQL = strSQL & vbCrLf & "  @strInputOutput varchar(20) = " _
                                                              & "Null OUTPUT,"
          strSQL = strSQL & vbCrLf & "  @strOutput      varchar(20) = " _
                                                              & "Null OUTPUT"
          strSQL = strSQL & vbCrLf & "AS"
          strSQL = strSQL & vbCrLf & "BEGIN"
          strSQL = strSQL & vbCrLf & "  SET NOCOUNT ON /* stops messages */"
          strSQL = strSQL & vbCrLf & "  DECLARE @intReturn int " _
                                                      & "/* Declare return */"
          strSQL = strSQL & vbCrLf & "  SELECT @intReturn = 43 " _
                                                      & "/* Set the return */"
          strSQL = strSQL & vbCrLf & "  SELECT @strInputOutput = " _
                                                      & "'Param InOut Test'"
          strSQL = strSQL & vbCrLf & "  SELECT @strOutput = 'Param Out Test'"
          strSQL = strSQL & vbCrLf & "  RETURN @intReturn"
          strSQL = strSQL & vbCrLf & "END"
          MsgBox strSQL
          db.Execute strSQL, dbSQLPassThrough
   
          'Get ready to call procedure.
          'Declare the variables in SQL and then set them
          'in SQL code. Then retrieve the values as a recordset.
          strSQL = "SET NOCOUNT ON /* stops unwanted messages */"
          strSQL = strSQL & vbCrLf & "/* Declare the variables */"
          strSQL = strSQL & vbCrLf & "DECLARE @intIn       int"
          strSQL = strSQL & vbCrLf & "DECLARE @strInOut     varchar(20)"
          strSQL = strSQL & vbCrLf & "DECLARE @strOut      varchar(20)"
          strSQL = strSQL & vbCrLf & "DECLARE @intRet      int"
          strSQL = strSQL & vbCrLf & "/* Populate In Parameters */"
          strSQL = strSQL & vbCrLf & "SELECT @intIn = 5"
          strSQL = strSQL & vbCrLf & "SELECT @strInOut = 'In/Out In'"
          strSQL = strSQL & vbCrLf & "/* Execute the procedure */"
          strSQL = strSQL & vbCrLf & "EXECUTE @intRet = sp_ReturnParams "
          strSQL = strSQL & "@intIn, @strInOut OUTPUT, @strOut OUTPUT"
          strSQL = strSQL & vbCrLf & "/* Select back the records */"
          strSQL = strSQL & vbCrLf & "SELECT @intRet AS param1, @intIn "
          strSQL = strSQL & "AS param2, @strInOut AS param3, @strOut AS _
                                                           param4"
          Set rs = db.OpenRecordset(strSQL, dbOpenSnapshot, dbSQLPassThrough)
   
          'Display the data in the parameters in a messagebox
          strResult = "intReturn = " & rs.Fields("param1")
          strResult = strResult & vbCrLf & "intInPut = " & rs.Fields("param2")
          strResult = strResult & vbCrLf & "strInPutOutput = " & _
                                                           rs.Fields("param3")
          strResult = strResult & vbCrLf & "strOutput = " & _
                                                           rs.Fields("param4")
          MsgBox strResult
       End Sub
   
   

5. In the ODBC Administrator applet, create a DSN named DSN_SP_TEST that connects to an SQL Server that you have the necessary rights to.

6. Run the project. The code should connect to the server, create a stored procedure named dbo.sp_ReturnParams, execute it passing in some values, and display a message box with the return parameters.

REFERENCES