HOWTO: Use the ODBC API Function SQLExecDirect with RDO

• Microsoft Visual Basic Control Creation, Learning Professional and Enterprise Editions for Windows, version 5.0
• Enterprise Edition of Microsoft Visual Basic, 32-bit only, for Windows, version 4.0

SUMMARY

Because RDO exposes the hEnv, hDbc, and hStmt properties of the ODBC API to the programmer, you are able to utilize ODBC API calls in conjunction with RDO. This can be helpful if RDO does not implement a feature of the ODBC API that you would like to use.

This article gives an example of how to use the ODBC API SQLExecDirect function in combination with the RDO rdoConnection.hDbc property to execute SQL without the use of the rdoConnection.Execute method.

MORE INFORMATION

Programming directly to the ODBC API gives you an alternative to using RDO and DAO code to access your ODBC database. This direct method allows the programmer to have low-level control over the ODBC datasource, but introduces the Visual Basic 4.0 programmer to a complex programming model that requires in-depth knowledge of the ODBC 2.0 specification.

If you feel that you can benefit from this direct approach, before you proceed you should obtain a copy of the ODBC 2.0 Programmer's Reference and SDK Guide that fully documents the ODBC API.

Sample Program

This example uses the ODBC API SQLExecDirect function in combination with the rdoConnection.hDbc property to execute SQL without the use of the RDO Execute method. It uses SQL Server and the Pubs database, but you can change the DSN and SQL to match your ODBC database.

1. Start a new project in Visual Basic. Form1 is created by default.

2. Add a Command button, Command1, to Form1.

3. Paste the following code into the General Declarations section of Form1:

         Option Explicit
         Private Declare Function SQLAllocStmt Lib "odbc32.dll" _
           (ByVal hdbc&, phstmt&) As Integer
         Private Declare Function SQLExecDirect Lib "odbc32.dll" _
           (ByVal hstmt&, ByVal szSqlStr$, ByVal cbSqlStr&) As Integer
   
         Private Sub Command1_Click()
           Dim cn As rdoConnection
           Set cn = rdoEnvironments(0).OpenConnection( _
             dsName:="MyServer", _
             Prompt:=rdDriverNoPrompt, _
             ReadOnly:=False)                            'get hDbc
   
           Dim rv As Integer                             'return value
           Dim lhStmt As Long                            'hStmt
           Dim szSql As String                           'SQL string
   
           szSql = "Select * into newtable from titles"  'create table SQL
           rv = SQLAllocStmt(cn.hdbc, lhStmt)            'allocate a statement
           Debug.Print GetRetCodeText(rv)                'print return value
                                                         'text
           rv = SQLExecDirect(lhStmt, szSql, Len(szSql)) 'execute the SQL
           Debug.Print GetRetCodeText(rv)                'print return value
                                                         'text
         End Sub
   
         Private Function GetRetCodeText(retcode As Integer)
           'get the return value text using ODBC32.TXT constants
           Dim x As String
           Select Case retcode
             Case -1: x = "SQL_ERROR"
             Case -2: x = "SQL_INVALID_HANDLE"
             Case 100: x = "SQL_NO_DATA_FOUND"
             Case 0: x = "SQL_SUCCESS"
             Case 1: x = "SQL_SUCCESS_WITH_INFO"
           End Select
           GetRetCodeText = x
         End Function
   
      NOTE: You will need to change the DSN to match yours before continuing.
   
   

4. Start the program or press the F5 key.

5. Click the Command1 button to execute the RDO and ODBC API code. If it executes successfully, SQL_SUCCESS will be output twice to the debug window and you will have a new table named newtable.

REFERENCES

Building Client/Server applications with Visual Basic Manual, Chapter 10, "Using the ODBC API."

ODBC 2.0 Programmer's Reference and SDK Guide, MS Press.

Hitchhiker's Guide to Visual Basic and SQL Server, Microsoft Press, ISBN: 1-55615-906-4.