三层架构之数据库访问层(VB)

''''########数据库访问层##########

''''返回一个ADOCN连接对象

''''与C#不同，这里不能关闭连接及释放内存
Public Function GetCN(sDBPath As String) As ADODB.Connection

   
    Const sPro As String = "provider=microsoft.jet.oledb.4.0;data source="
    Const sDBPWD As String = ";jet oledb:database password=QQ:48403849"
   
    Dim sDBPath As String
    Dim m_cn As ADODB.Connection
   
   
   
    Set m_cn = New ADODB.Connection
   
    m_cn.CursorLocation = adUseClient ''''客户端游标
   
    If m_cn.State <> adStateClosed Then m_cn.Close
   
    On Error GoTo conerr
   
    m_cn.Open sPro & sDBPath & sDBPWD
   
    Set GetCN = m_cn

    Exit Function
conerr:
    Set GetCN = Nothing
    MsgBox "数据库连接错误", vbCritical

End Function

''''执行一句SQL语句，正确返回 1
Public Function ExcuteSQL(sSQL As String) As Integer
    Dim m_cn As New ADODB.Connection
   
    On Error GoTo err
   
    Set m_cn = GetCN(sG_DBPath)
    m_cn.Execute sSQL
    m_cn.Close
    Set m_cn = Nothing
    ExcuteSQL = 1
   
    Exit Function
err:
    ExcuteSQL = 0
    Set m_cn = Nothing
   

End Function
''''执行一组SQL语句，正确返回1
Public Function ExcuteSQLEX(sSQL() As String) As Integer
    ''''调用事务处理
    Dim m_cn As New ADODB.Connection, i As Integer
   
    If UBound(sSQL) < 0 Then Exit Function
    On Error GoTo err
   
    Set m_cn = GetCN(sG_DBPath)
   
    m_cn.BeginTrans
    For i = 0 To UBound(sSQL) - 1
        m_cn.Execute sSQL(i)
    Next i
   
    m_cn.CommitTrans
    m_cn.Close
    Set m_cn = Nothing
   
    ExcuteSQLEX = 1
   
    Exit Function
err:
    ExcuteSQLEX = 0
    m_cn.RollbackTrans
    m_cn = Nothing
   
End Function

''''未完，待补充
 

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