'數(shù)據(jù)源信息常量 Public Const conn As String = "Provider = SQLOLEDB.1;Password = sa; UserID = sa; Initial Catalog = StudentFiles; Data Source = localhost" Public Const CONNECT_LOOP_MAX = 10 '一次執(zhí)行connect操作，可以訪問數(shù)據(jù)庫的次數(shù) Private IsConnect As Boolean '標記數(shù)據(jù)庫是否連接 Private Connect_Num As Integer '標記執(zhí)行Connect()函數(shù)后訪問數(shù)據(jù)的次數(shù) Private cnn As ADDODB.Connection '連接數(shù)據(jù)庫的Connect對象  Private re As ADDODB.Recordset '保存結(jié)果集的Recordset對象//連接數(shù)據(jù)庫 Private Sub Connect() '如果連接標記為真，則返回。 IF IsConnect = True Then    Exit Sub End If Set cnn = New ADODB.Connection '關(guān)鍵new用于創(chuàng)建新對象cnn  cnn.ConnectionString = conn  cnn.Open '判斷連接的狀態(tài) If cnn.State <> adStateOpen Then   MsgBox"數(shù)據(jù)庫連接失敗"   End End If '設(shè)置連接標識，表示已經(jīng)連接到數(shù)據(jù)庫 IsConnect = TrueEnd Sub'斷開與數(shù)據(jù)庫的連接Private Sub DisConnect() Dim rc As Long If IsConnect = False Then   Exit Sub End If '關(guān)閉連接 cnn.Close '釋放cnn Set cnn = Nothing IsConnect = FalseEnd Sub'使用Connect_Num控制數(shù)據(jù)連接Public Sub DB_Connect()  Connect_Num = Connect_Num + 1  ConnectEnd Sub'使用Connect_Num控制數(shù)據(jù)斷開Public Sub DB_Disconnect()If Connect_Num >= CONNECT_LOOP_MAX Then  Connect_Num = 0  Disconnect End If End Sub'強制關(guān)閉api方式訪問俄的數(shù)據(jù)庫，計數(shù)器復(fù)位Public Sub DBapi_Disconnect()  Connect_Num = 0  DisconnectEnd Sub'執(zhí)行數(shù)據(jù)庫操作語言'byval 就是按參數(shù)的值傳遞，再傳遞過程中，參數(shù)不會發(fā)生變化(也就是將參數(shù)值而不是將地址傳遞給過程的方式，這就使過程訪問發(fā)哦變量的副本，過程不可改變變量的值)；與之對應(yīng)的是byref,指按參數(shù)的地址傳值，byref可以省略Public Sub SQLExt(ByVal TmpSQLstmt As String )    Dim cmd As New ADODB.Command '創(chuàng)建Command對象cmd    DB_Connect '連接數(shù)據(jù)庫    Set cmd.ActiveConnection = cnn '設(shè)置cmd的ActiveConnect屬性，指定與其關(guān)聯(lián)的數(shù)據(jù)庫連接  cmd.CommandText = TmpSQLstmt '設(shè)置要執(zhí)行的命令文本  'MsgBox TmpSQLstmt  cmd.Execute '執(zhí)行命令  Set cmd = Nothing  DB_DisConnect '斷開與數(shù)據(jù)庫的連接End Sub'執(zhí)行數(shù)據(jù)庫查詢語句Public Function QueryExt(ByVal TmpSQLstmt As String ) As ADODB.Recordset    Dim rst As New ADODB.Recordset '創(chuàng)建Rescordset對象rst  DB_Connect '連接數(shù)據(jù)庫  Set rst.ActiveConnection = cnn '設(shè)置rst的ActiveConnection屬性,指定與其相關(guān)的數(shù)據(jù)庫的連接  rst.CursorType = adOpenDynamic '設(shè)置游標類型  rst.LockType = adLockOptimistic '設(shè)置鎖定類型  rst.Open TmpSQLstmt '打開記錄集  Set QueryExt = rst '返回記錄集  End Function