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Wild Cat
Wild Cat

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Connect MS Access to SQL Server using ADO

#vba

Summary

This article explains how to connect MS Access to SQL Server using ADO. It also covers how to measure and compare performance across different CursorLocation, CursorType, and LockType settings.

Common procedures

The following reference needs to be added to the VBA project references.
Microsoft ActiveX Data Objects x.x Library

'Set values of SQL Server
Private Const ServerName   As String = "myServerName"
Private Const DatabaseName As String = "myDatabaseName"
Private Const UserID       As String = "myID"
Private Const Password     As String = "myPassword"

Public Sub OpenConnection(ByRef cn As ADODB.Connection)    
    cn.ConnectionTimeout = 100 '100 seconds
    cn.CommandTimeout = 100    '100 seconds

    '# SQL Server Authentication Mode
    cn.ConnectionString = "Provider=SQLOLEDB;" & _
                          "Server=" & ServerName & ";" & _
                          "Database=" & DatabaseName & ";" & _
                          "USER ID=" & UserID & ";" & _
                          "PASSWORD=" & Password & ";"

    '# Windows Authentication Mode
    'cn.ConnectionString = "Provider=SQLOLEDB;" & _
    '                      "Server=" & ServerName & ";" & _
    '                      "Database=" & DatabaseName & ";" & _
    '                      "Integrated Security=SSPI;"

    cn.Open    
End Sub

Public Sub OpenRecordsetToRead(ByRef cn As ADODB.Connection, _
                               ByRef rs As ADODB.Recordset, _
                               ByVal sql As String)
    rs.CursorLocation = adUseServer
    rs.CursorType = adOpenForwardOnly
    rs.LockType = adLockReadOnly
    rs.ActiveConnection = cn
    rs.Source = sql
    rs.Open
End Sub

Public Sub OpenRecordsetToUpdate(ByRef cn As ADODB.Connection, _
                                 ByRef rs As ADODB.Recordset, _
                                 ByVal sql As String)
    rs.CursorLocation = adUseServer
    rs.CursorType = adOpenKeyset
    rs.LockType = adLockOptimistic
    rs.ActiveConnection = cn
    rs.Source = sql
    rs.Open
End Sub

Public Sub CloseRecordset(ByRef rs As ADODB.Recordset)
    If Not rs Is Nothing Then
        If rs.State = adStateOpen Then rs.Close
        Set rs = Nothing
    End If
End Sub

Public Sub CloseConnection(ByRef cn As ADODB.Connection)
    If Not cn Is Nothing Then
        If cn.State = adStateOpen Then cn.Close
        Set cn = Nothing
    End If
End Sub
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Microsoft documentation on ConnectionString of ADODB.Connection
Microsoft OLE DB Provider for SQL Server Overview

Use SQL SELECT statement

Note: The following code utilizes the common procedures provided at the top of this page.

Public Sub GetRecordset()

    On Error GoTo ErrHandler

    Dim sql As String

    Dim cn As New ADODB.Connection
    Dim rs As New ADODB.Recordset

    sql = "SELECT * FROM TEST_TABLE"

    Call OpenConnection(cn)
    Call OpenRecordsetToRead(cn, rs, sql)

    If rs Is Nothing Or (rs.BOF And rs.EOF) Then
        Exit Sub
    End If

    Do Until rs.EOF
        Debug.Print rs.Fields(0).Value 'Show 1st filed of table
        Debug.Print rs.Fields(1).Value 'Show 2nd filed of table
        rs.MoveNext
    Loop

    Call CloseRecordset(rs)
    Call CloseConnection(cn)

    Exit Sub

ErrHandler:
    Call CloseRecordset(rs)
    Call CloseConnection(cn)
    Debug.Print "ErrNumber:" & Err.Number & " " & Err.Description

End Sub
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Use SQL statement of INSERT, UPDATE and DELETE

Note: The following code utilizes the common procedures provided at the top of this page.

Public Sub ExecuteSQL()

    On Error GoTo ErrHandler

    Dim cn As New ADODB.Connection
    Dim sql As String

    Call OpenConnection(cn)

    sql = "INSERT INTO TEST_TABLE (No, FirstName, LastName) Values(1,'John','Smith')"

    'cn.BeginTrans '#Begin transaction    
    cn.Execute sql    
    'cn.CommitTrans '#Commit transaction

    Call CloseConnection(cn)

    Exit Sub

ErrHandler:
    'cn.RollbackTrans '#Rollback
    Call CloseConnection(cn)
    Debug.Print "ErrNumber:" & Err.Number & " " & Err.Description
End Sub
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Properties of ADODB.Recordset

ADODB.Recordset has three properties to set.

  • CursorLocation
  • CursorType
  • LockType

Microsoft documentation on ADO settings

If the properties are configured incorrectly, they will be automatically adjusted to the appropriate settings.

The actual properties returned to your application depend on the data provider and the database.

The following table illustrates how these properties are modified in my environment. The properties modified are highlighted in red.

The following code generates this table.

Note1: The following code utilizes the common procedures provided at the top of this page.

Note2:The code below measures execution time by reading all table records. I suggest testing this with a smaller table first to avoid long wait times.

Public Sub OutputAdoRecordsetProperty()

    On Error GoTo ErrHandler

    Dim cn As New ADODB.Connection
    Dim rs As New ADODB.Recordset
    Dim arrayCursorLocation() As Variant
    Dim arrayCursorType()     As Variant
    Dim arrayLockType()       As Variant
    Dim currentCursorLocation As Variant
    Dim currentCursorType     As Variant
    Dim currentLockType       As Variant
    Dim fieldsResult          As String
    Dim currentResult         As String
    Dim filePathResult        As String
    Dim startTime             As Double
    Dim endTime               As Double
    Dim executionTime         As Double
    Dim currentField          As Long
    Dim currentValue          As Variant

    arrayCursorLocation = Array(adUseClient, adUseServer)

    arrayCursorType = Array(adOpenDynamic, _
                            adOpenForwardOnly, _
                            adOpenKeyset, _
                            adOpenStatic)

    arrayLockType = Array(adLockBatchOptimistic, _
                          adLockOptimistic, _
                          adLockPessimistic, _
                          adLockReadOnly)

    filePathResult = CurrentProject.Path & "\AdoRsPropertyAbility.csv"

    fieldsResult = "Setting CursorLocation," & _
                   "Setting CursorType," & _
                   "Setting LockType," & _
                   "Actual CursorLocation," & _
                   "Actual CursorType," & _
                   "Actual LockType," & _
                   "adAddNew," & _
                   "adApproxPosition," & _
                   "adBookmark," & _
                   "adDelete," & _
                   "adFind," & _
                   "adHoldRecords," & _
                   "adIndex," & _
                   "adMovePrevious," & _
                   "adNotify," & _
                   "adResync," & _
                   "adSeek," & _
                   "adUpdate," & _
                   "adUpdateBatch," & _
                   "RecordCount, " & _
                   "Execution time"

    Call WriteCurrentResult(filePathResult, fieldsResult)

    Dim sql As String
    sql = "SELECT * FROM TEST_TABLE"

    For Each currentCursorLocation In arrayCursorLocation
        For Each currentCursorType In arrayCursorType
            For Each currentLockType In arrayLockType

                Call OpenConnection(cn)

                startTime = Timer

                rs.CursorLocation = currentCursorLocation
                rs.CursorType = currentCursorType
                rs.LockType = currentLockType
                rs.ActiveConnection = cn
                rs.Source = sql
                rs.Open

                'Setting Cursor Location
                currentResult = GetCursorLocation(currentCursorLocation) & ","

                'Setting CursorType
                currentResult = currentResult & GetCursorType(currentCursorType) & ","

                'Setting LockType
                currentResult = currentResult & GetLockType(currentLockType) & ","

                'Actual  CursorLocation
                currentResult = currentResult & GetCursorLocation(rs.CursorLocation) & ","

                'Actual  CursorType
                currentResult = currentResult & GetCursorType(rs.CursorType) & ","

                'Actual  LockType
                currentResult = currentResult & GetLockType(rs.LockType) & ","

                'CursorOptionEnum adAddNew
                currentResult = currentResult & rs.Supports(adAddNew) & ","

                'CursorOptionEnum adApproxPosition
                currentResult = currentResult & rs.Supports(adApproxPosition) & ","

                'CursorOptionEnum adBookmark
                currentResult = currentResult & rs.Supports(adBookmark) & ","

                'CursorOptionEnum adDelete
                currentResult = currentResult & rs.Supports(adDelete) & ","

                'CursorOptionEnum adFind
                currentResult = currentResult & rs.Supports(adFind) & ","

                'CursorOptionEnum adHoldRecords
                currentResult = currentResult & rs.Supports(adHoldRecords) & ","

                'CursorOptionEnum adIndex
                currentResult = currentResult & rs.Supports(adIndex) & ","

                'CursorOptionEnum adMovePrevious
                currentResult = currentResult & rs.Supports(adMovePrevious) & ","

                'CursorOptionEnum adNotify
                currentResult = currentResult & rs.Supports(adNotify) & ","

                'CursorOptionEnum adResync
                currentResult = currentResult & rs.Supports(adResync) & ","

                'CursorOptionEnum adSeek
                currentResult = currentResult & rs.Supports(adSeek) & ","

                'CursorOptionEnum adUpdate
                currentResult = currentResult & rs.Supports(adUpdate) & ","

                'CursorOptionEnum adUpdateBatch
                currentResult = currentResult & rs.Supports(adUpdateBatch) & ","

                'RecordCount
                currentResult = currentResult & rs.RecordCount & ","

                'Measure execution time
                Do Until rs.EOF
                    For currentField = 0 To rs.Fields.Count - 1
                        currentValue = rs.Fields(currentField).Value
                    Next
                    rs.MoveNext
                Loop
                endTime = Timer
                executionTime = endTime - startTime
                currentResult = currentResult & executionTime

                Call CloseRecordset(rs)

                Call WriteCurrentResult(filePathResult, currentResult)

                Call CloseConnection(cn)

            Next currentLockType
        Next currentCursorType
    Next currentCursorLocation

    MsgBox "Output has been completed.", vbInformation

    Exit Sub

ErrHandler:
    Call CloseRecordset(rs)
    Call CloseConnection(cn)
    MsgBox "ErrNumber:" & Err.Number & " " & Err.Description

End Sub

Private Function GetCursorLocation(ByVal lngCursorLocation As Long) As String
    Select Case lngCursorLocation
        Case 2
            GetCursorLocation = "adUseServer"
        Case 3
            GetCursorLocation = "adUseClient"
    End Select
End Function

Private Function GetCursorType(ByVal lngCursorType As Long) As String
    Select Case lngCursorType
        Case 0
            GetCursorType = "adOpenForwardOnly"
        Case 1
            GetCursorType = "adOpenKeyset"
        Case 2
            GetCursorType = "adOpenDynamic"
        Case 3
            GetCursorType = "adOpenStatic"
    End Select
End Function

Private Function GetLockType(ByVal lngLockType As Long) As String
    Select Case lngLockType
        Case 1
            GetLockType = "adLockReadOnly"
        Case 2
            GetLockType = "adLockPessimistic"
        Case 3
            GetLockType = "adLockOptimistic"
        Case 4
            GetLockType = "adLockBatchOptimistic"
    End Select
End Function

Private Sub WriteCurrentResult(ByVal filePathResult As String, _
                               ByVal currentResult As String)
    Open filePathResult For Append As #1
    Print #1, currentResult
    Close #1
End Sub
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Connect to SQL Server using ADO And ODBC connection string

The code below shows how to connect to SQL Server using ADO And an ODBC connection string.

It is not intended for standalone tables in SQL Server. Rather, it manages the connection between Access tables and SQL Server tables, as in the following example.

  • Select records by joining Access tables with SQL Server tables.
  • Insert records from an Access table into a SQL Server table. 
'Set values of SQL Server
Private Const ServerName   As String = "myServerName"
Private Const DatabaseName As String = "myDatabaseName"
Private Const UserID       As String = "myID"
Private Const Password     As String = "myPassword"

'Create ODBC connection string
Public Function GetConODBC() As String
    GetConODBC = _
        "[ODBC" & _
        ";DRIVER=SQL Server" & _
        ";SERVER=" & ServerName & _
        ";DATABASE=" & DatabaseName & _
        ";UID=" & UserID & _
        ";PWD=" & Password & _
        "]."
End Function

'Get records using ADO and ODBC connection string
Public Sub GetRecordset_ADO_ODBC()

    Dim sql As String

    Dim cn As ADODB.Connection
    Dim rs As New ADODB.Recordset

    Set cn = CurrentProject.Connection

    sql = "SELECT * FROM " & GetConODBC & "SQLServerTable;"

    rs.Open sql, cn

    Do Until rs.EOF
        Debug.Print rs.Fields(0).Value 'Show 1st filed of table
        Debug.Print rs.Fields(1).Value 'Show 2nd filed of table
        rs.MoveNext
    Loop

    rs.Close
    cn.Close

End Sub

'Get records by joining Access table with SQLServer table
Public Sub GetRecordsetByJoiningAccessWithSQLServer_ADO_ODBC()

    Dim sql As String

    Dim cn As ADODB.Connection
    Dim rs As New ADODB.Recordset

    Set cn = CurrentProject.Connection

    sql = _
        "SELECT AccessTable.A, SQLServerTable.B " & _
        "FROM AccessTable " & _
        "LEFT JOIN " & GetConODBC & "SQLServerTable " & _
        "ON AccessTable.ID = SQLServerTable.ID;"

    rs.Open sql, cn

    Do Until rs.EOF
        Debug.Print rs.Fields(0).Value 'Show 1st filed of table
        Debug.Print rs.Fields(1).Value 'Show 2nd filed of table
        rs.MoveNext
    Loop

    rs.Close
    cn.Close

End Sub

'Insert into SQL Server table from Access table
Public Sub InsertIntoSQLServerFromAccess_ADO_ODBC()

    Dim sql As String

    Dim cn As ADODB.Connection

    Set cn = CurrentProject.Connection

    sql = _
        "INSERT INTO " & GetConODBC & "SQLServerTable " & _
        "SELECT * FROM AccessTable;"

    cn.Execute sql

    cn.Close

End Sub
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