7/16/2014 Microsoft Access tips: ADO Programming Code Examples

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Microsoft Access: ADO Programming Code Examples

Provided by Allen Browne, March 2007. Updated May 2009.

ADO Programming Code Examples

This page is a reference for developers, demonstrating how to use the ADO library to list and manipulate the objects in Access.

ADO (ActiveX Data Objects) is more generic than DAO (the one designed to handle the objects in Access), so supports features of

databases other than Access. In the wider world beyond Access, ADO has largely been replaced by the quite different ADO.NET

library.

In general, DAO is preferred over ADO, but there are some operations that work under ADO only. In general, these work in code

only. They will not work if you try them in the Query window, since Access itself uses DAO. They also require JET 4 (Access 2000 or

later.)

ADO provides only limited ways to manipulate the data structure (typically via DDL query statements), unless you also use the ADOX

library which provides the extensions to get to the database catalog.

To use the ADO Library, choose References on the Tools menu in the code window, and check the box beside: Microsoft ActiveX Data Objects 2.x Library

There is no explanation of the code beyond in-line comments, and no error handling in most examples.

Index of Functions Description

ShowSchema() List the tables

AdoRecordsetExample() Open a recordset

CreateViewAdo() Create a new query

ModifyViewAdo() Modify a query

ShowBand() Illustrate the BAND operator with literals. (ADO only.)

TestBnot() Illustrate BNOT (binary NOT) operator (ADO only.)

TestBand() Illustrate BAND (binary AND) operator. (ADO only.)

ShowUserRosterMultipleUsers() List the users currently connected to the database.

UserCount() Count the number of distinct users connected to the database.

ExecuteADO() Execute an action query with ADO, and know how many records were inserted/deleted/changed.

Option Compare DatabaseOption Explicit

Function ShowSchema() 'Purpose: List the tables, using ADO. Dim cn As ADODB.Connection Dim rs As ADODB.Recordset Dim i As Integer Set cn = CurrentProject.Connection Set rs = cn.OpenSchema(adSchemaTables, Array(Empty, Empty, Empty, "TABLE"))' For i = 0 To rs.Fields.Count - 1' Debug.Print rs.Fields(i).Name' Next

Do While Not rs.EOF Debug.Print rs.Fields("TABLE_NAME").Value rs.MoveNext Loop

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rs.Close Set rs = Nothing Set cn = NothingEnd Function

Function AdoRecordsetExample() 'Purpose: Open a recordset using ADO. Dim rs As New ADODB.Recordset Dim strSql As String strSql = "SELECT MyField FROM MyTable;" rs.Open strSql, CurrentProject.Connection Do While Not rs.EOF Debug.Print rs!MyField rs.MoveNext Loop rs.Close Set rs = NothingEnd Function

Function CreateViewAdo() 'Purpose: Create a new query using ADO. Dim cn As ADODB.Connection Dim strSql As String strSql = "CREATE VIEW MyTableView AS SELECT MyTable.* FROM MyTable;" Set cn = CurrentProject.Connection cn.Execute strSql Debug.Print "MyTableView created" Set cn = NothingEnd Function

Function ModifyViewAdo() 'Purpose: Modify a query using ADO. Dim cn As ADODB.Connection Dim strSql As String strSql = "ALTER TABLE Query1 AS SELECT MyTable.* FROM MyTable;" Set cn = CurrentProject.Connection cn.Execute strSql Debug.Print "MyTableView modified" Set cn = NothingEnd Function

Function ShowBand() Dim rs As New ADODB.Recordset rs.Open "SELECT (2 BAND 4) AS Result;", CurrentProject.Connection ShowBand = rs!Result rs.Close Set rs = NothingEnd Function

Function TestBnot() 'Purpose: Illustrate BNOT (binary NOT) operator (ADO only.) Dim cn As ADODB.Connection Dim strSql As String Dim lngKt As Long Set cn = CurrentProject.Connection strSql = "UPDATE MyTable SET MyIntFlip = BNOT MyInt WHERE MyIntFlip Is Not Null;"

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cn.Execute strSql, lngKt Set cn = Nothing TestBnot = lngKtEnd Function

Function TestBand() 'Purpose: Illustrate BAND (binary AND) operator. (ADO only.) Dim rs As New ADODB.Recordset Dim strSql As String strSql = "SELECT MyBitField, (MyBitField BAND 2) 0 As MyResult FROM MyTable;" rs.Open strSql, CurrentProject.Connection Do While Not rs.EOF Debug.Print rs!MyBitfield, rs!MyResult rs.MoveNext Loop rs.Close Set rs = NothingEnd FunctionFunction ShowUserRosterMultipleUsers() 'Source: kb 198755. Dim cn As New ADODB.Connection 'Dim cn2 As New ADODB.Connection Dim rs As New ADODB.Recordset Dim i, j As Long

cn.Provider = "Microsoft.Jet.OLEDB.4.0" cn.Open "Data Source=C:\Data\Northwind2003.mdb"

'cn2.Open "Provider=Microsoft.Jet.OLEDB.4.0;" & "Data Source=C:\Data\Northwind2003.mdb"

' The user roster is exposed as a provider-specific schema rowset ' in the Jet 4 OLE DB provider. You have to use a GUID to ' reference the schema, as provider-specific schemas are not ' listed in ADO's type library for schema rowsets

Set rs = cn.OpenSchema(adSchemaProviderSpecific, , "{947bb102-5d43-11d1-bdbf-00c04fb92675}")

'Output the list of all users in the current database.

Debug.Print rs.Fields(0).Name, "", rs.Fields(1).Name, "", rs.Fields(2).Name, rs.Fields(3).Name

While Not rs.EOF Debug.Print rs.Fields(0), rs.Fields(1), rs.Fields(2), rs.Fields(3) rs.MoveNext WendEnd Function

Function UserCount() As Long Dim cnLocal As ADODB.Connection 'Current project connection. Dim cnBackEnd As New ADODB.Connection 'Connection to back end database. Dim rsBEUserRoster As New ADODB.Recordset 'JET User Roster for back end database. Dim rsTarget As New ADODB.Recordset 'Temp table to record users and de-dupe. Dim strPath As String 'Full path to back end. Dim strSql As String 'SQL string. Dim lngKt As Long 'Loop controller. Dim dtEnteredOn As Date 'Current date and time. 'Set this to the full path of your back end database. strPath = "C:\Data\Northwind2003.mdb"

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'Open the JET User Roster for the back end.

cnBackEnd.Provider = "Microsoft.Jet.OLEDB.4.0" cnBackEnd.Open "Data Source=" & strPath Set rsBEUserRoster = cnBackEnd.OpenSchema(adSchemaProviderSpecific, , _ "{947bb102-5d43-11d1-bdbf-00c04fb92675}") 'Clear temp table, and copy the user roster in. dtEnteredOn = Now() Set cnLocal = CurrentProject.Connection cnLocal.Execute "DELETE FROM tzJetUserRoster;" rsTarget.Open "tzJetUserRoster", cnLocal, adOpenDynamic, adLockOptimistic Do While Not rsBEUserRoster.EOF rsTarget.AddNew For lngKt = 0 To 3 rsTarget(lngKt) = rsBEUserRoster(lngKt) rsTarget!EnteredOn = dtEnteredOn Next rsTarget.Update rsBEUserRoster.MoveNext Loop rsTarget.Close rsBEUserRoster.Close cnBackEnd.Close 'Get the count of the number of distinct users who are connected. strSql = "SELECT DISTINCT Computer_Name FROM tzJetUserRoster WHERE Connected = True;" Set rsTarget = New ADODB.Recordset rsTarget.Open strSql, cnLocal, adOpenKeyset If Not (rsTarget.BOF And rsTarget.EOF) Then rsTarget.MoveLast UserCount = rsTarget.RecordCount End If rsTarget.Close 'Dereference objects Set rsTarget = Nothing Set rsBEUserRoster = Nothing Set cnLocal = Nothing Set cnBackEnd = NothingEnd Function

Function ExecuteADO() As Long 'Purpose: How to execute an action query with ADO. 'Return: Number of records affected by action query. Dim strSql As String Dim lngKt As Long strSql = "INSERT INTO tblClient (Surname, FirstName ) " & _ "SELECT 'Smith' AS Surname, 'Jim' AS FirstName;" CurrentProject.Connection.Execute strSql, lngKt ExecuteADO = lngKtEnd Function

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