Article ID: 168336
Article Last Modified on 3/2/2005
APPLIES TO
- Microsoft ActiveX Data Objects 1.0
- Microsoft ActiveX Data Objects 1.5
- Microsoft ActiveX Data Objects 2.0
- Microsoft ActiveX Data Objects 2.1 Service Pack 2
- Microsoft ActiveX Data Objects 2.5
- Microsoft ActiveX Data Objects 2.6
- Microsoft ActiveX Data Objects 2.7
- Microsoft Visual Basic 5.0 Professional Edition
- Microsoft Visual Basic 6.0 Professional Edition
- Microsoft Visual Basic 5.0 Enterprise Edition
- Microsoft Visual Basic 6.0 Enterprise Edition
This article was previously published under Q168336
For a Microsoft Visual Basic .NET version of this article, see 310985.
SUMMARY
ActiveX Data Objects (ADO) offers several ways to open both the Connection and Recordset objects. This article presents sample code for several common techniques for each object.
MORE INFORMATION
There are several ways to open a Connection Object within ADO:
- By Setting the ConnectionString property to a valid Connect string and then calling the Open() method. This connection string is provider- dependent.
- By passing a valid Connect string to the first argument of the Open() method.
- By passing a valid Command object into the first argument of a Recordset's Open method.
- By passing the ODBC Data source name and optionally user-id and password to the Connection Object's Open() method.
There are three ways to open a Recordset Object within ADO:
- By opening the Recordset off the Connection.Execute() method.
- By opening the Recordset off the Command.Execute() method.
- By opening the Recordset object without a Connection or Command object, and passing an valid Connect string to the second argument of the Recordset.Open() method.
This code assumes that Nwind.mdb is installed with Visual Basic, and is located in the C:\Program Files\DevStudio\VB directory:
Option Explicit Private Sub cmdOpen_Click() Dim Conn1 As New adodb.Connection Dim Cmd1 As New adodb.Command Dim Errs1 As Errors Dim Rs1 As New adodb.Recordset Dim i As Integer Dim AccessConnect As String ' Error Handling Variables Dim errLoop As Error Dim strTmp As String AccessConnect = "Driver={Microsoft Access Driver (*.mdb)};" & _ "Dbq=nwind.mdb;" & _ "DefaultDir=C:\program files\devstudio\vb;" & _ "Uid=Admin;Pwd=;" '--------------------------- ' Connection Object Methods '--------------------------- On Error GoTo AdoError ' Full Error Handling which traverses ' Connection object ' Connection Open method #1: Open via ConnectionString Property Conn1.ConnectionString = AccessConnect Conn1.Open Conn1.Close Conn1.ConnectionString = "" ' Connection Open method #2: Open("[ODBC Connect String]","","") Conn1.Open AccessConnect Conn1.Close ' Connection Open method #3: Open("DSN","Uid","Pwd") Conn1.Open "Driver={Microsoft Access Driver (*.mdb)};" & _ "DBQ=nwind.mdb;" & _ "DefaultDir=C:\program files\devstudio\vb;" & _ "Uid=Admin;Pwd=;" Conn1.Close '-------------------------- ' Recordset Object Methods '-------------------------- ' Don't assume that we have a connection object. On Error GoTo AdoErrorLite ' Recordset Open Method #1: Open via Connection.Execute(...) Conn1.Open AccessConnect Set Rs1 = Conn1.Execute("SELECT * FROM Employees") Rs1.Close Conn1.Close ' Recordset Open Method #2: Open via Command.Execute(...) Conn1.ConnectionString = AccessConnect Conn1.Open Cmd1.ActiveConnection = Conn1 Cmd1.CommandText = "SELECT * FROM Employees" Set Rs1 = Cmd1.Execute Rs1.Close Conn1.Close Conn1.ConnectionString = "" ' Recordset Open Method #3: Open via Command.Execute(...) Conn1.ConnectionString = AccessConnect Conn1.Open Cmd1.ActiveConnection = Conn1 Cmd1.CommandText = "SELECT * FROM Employees" Rs1.Open Cmd1 Rs1.Close Conn1.Close Conn1.ConnectionString = "" ' Recordset Open Method #4: Open w/o Connection & w/Connect String Rs1.Open "SELECT * FROM Employees", AccessConnect, adOpenForwardOnly Rs1.Close Done: Set Rs1 = Nothing Set Cmd1 = Nothing Set Conn1 = Nothing Exit Sub AdoError: i = 1 On Error Resume Next ' Enumerate Errors collection and display properties of ' each Error object (if Errors Collection is filled out) Set Errs1 = Conn1.Errors For Each errLoop In Errs1 With errLoop strTmp = strTmp & vbCrLf & "ADO Error # " & i & ":" strTmp = strTmp & vbCrLf & " ADO Error # " & .Number strTmp = strTmp & vbCrLf & " Description " & .Description strTmp = strTmp & vbCrLf & " Source " & .Source i = i + 1 End With Next AdoErrorLite: ' Get VB Error Object's information strTmp = strTmp & vbCrLf & "VB Error # " & Str(Err.Number) strTmp = strTmp & vbCrLf & " Generated by " & Err.Source strTmp = strTmp & vbCrLf & " Description " & Err.Description MsgBox strTmp ' Clean up gracefully without risking infinite loop in error handler On Error GoTo 0 GoTo Done End Sub
ERROR NOTES
Only the ADO Connection object has an errors collection. The observant reader will notice that a lightweight error handler is in effect for the RecordSet.Open examples. In the event of an error opening a RecordSet object, ADO should return the most explicit error from the OLEDB provider. Some common errors that can be encountered with the preceding code follow.
If you omit (or there is an error in) the DefaultDir parameter in the connect string, you may receive the following error:
If there is an error in the Dbq parameter in the connect string, you may receive the following error:
The preceding errors also populate the Connection.Errors collection with the following errors:
Note that for each error, the ADO Error number is the same, in this case translating to 0x80004005, which is the generic E_FAIL error message. The underlying Component did not have a specific error number for the condition encountered, but useful information was never-the-less raised to ADO.
REFERENCES
For additional information, click the following article number to view the article in the Microsoft Knowledge Base:
301216 How To Populate a DataSet Object from a Database by Using Visual Basic .NET
For additional information, click the article numbers below to view the articles in the Microsoft Knowledge Base:
188857 PRB: Use Open Method to Change CursorType and LockType
194979 INFO: ADO Spawns Additional Connections to SQL Server
168335 INFO: Using ActiveX Data Objects (ADO) via Visual Basic
193332 FILE: MDACCON.EXE Using Connection Strings with ODBC/OLEDB/ADO/RDS
Keywords: kbhowto KB168336