【正文】 ariant, ByVal LastCol As Integer)book_num = (0).CellValue()panduan = (7).CellValue()End SubPrivate Sub Form_Load()Dim rs_find As New Dim sql As Stringsql = select * from 圖書類別 sql, conn, adOpenKeyset, adLockPessimisticIf Not Then Do While Not (0) Loop = 0End IfEnd Sub　　查詢完畢后，輸出查詢結(jié)果，如圖24所示?！　　★@示目錄　　(6) 用戶登錄子窗體代碼　在本項(xiàng)目中，用戶登錄子窗體是運(yùn)行的第一個界面，它的作用是檢查用戶名和密碼是否正確。由于用戶的資料是存放在數(shù)據(jù)庫中，所以在啟動該子窗體時，就已經(jīng)連接了數(shù)據(jù)庫。其代碼如下:　　Private Sub Form_Load()　　Dim connectionstring As String　　connectionstring = provider=。 amp。 _　　data source=　　 connectionstring　　t = 0　　End Sub　　“確定”按鈕的作用是檢查輸入的數(shù)據(jù)是否與數(shù)據(jù)庫中的數(shù)據(jù)一致?！　rivate Sub Command1_Click()　　Dim sql As String　　Dim rs_login As New 　　If Trim() = Then ’ 判斷輸入的用戶名是否為空MsgBox 沒有這個用戶, vbOKOnly + vbExclamation, 　　　　Else　　sql = select * from 系統(tǒng)管理 where 用戶名=’ amp。 amp。 ’　　 sql, conn, adOpenKeyset, adLockPessimistic　　If = True Then　　MsgBox 沒有這個用戶, vbOKOnly + vbExclamation, 　　　　Else ’ 檢驗(yàn)密碼是否正確　　用戶名和密碼通過后，要關(guān)閉本窗體并打開主窗體?！　f Trim((1)) = Trim() Then　　userID = 　　userpow = (2)　　　　Unload Me　　　　Else　　MsgBox 密碼不正確, vbOKOnly + vbExclamation, 　　　　End If　　End If　　End If　　’ 只能輸入3次　　t = t + 1　　If t = 3 Then　　Unload Me　　End If　　Exit Sub　　End Sub （7）查詢借書信息如圖25如圖27代碼如下：Option ExplicitPrivate Sub Command1_Click()Dim sql As StringDim rs_find As New If = True Then sql = select * from 書籍信息 where 是否被借出=39。是39。End IfIf = True Then sql = select * from 書籍信息 where 是否被借出=39。否39。End IfIf = True Then sql = select * from 借閱信息 where 讀者姓名=39。 amp。 amp。 39。End If = adUseClient sql, conn, adOpenKeyset, adLockPessimistic = False = False = False Set = rs_findEnd SubPrivate Sub Command2_Click()Unload MeEnd SubPrivate Sub Frame2_DragDrop(Source As Control, X As Single, Y As Single)End Sub此板塊，可以查詢已經(jīng)借出的書，沒有借出的書，也可以按讀者姓名查詢?。。。?）還書信息如圖26如圖26代碼如下：Option ExplicitDim findform As BooleanPrivate Sub Combo1_Click() = End SubPrivate Sub Combo2_Click() = End SubPrivate Sub Combo3_Click() = End SubPrivate Sub Combo4_Click() = End SubPrivate Sub Command1_Click()Dim rs_reader As New Dim sql As Stringfindform = Truesql = select * from 借閱信息 where 讀者姓名=39。 amp。 amp。 39。 = adUseClient sql, conn, adOpenKeyset, adLockPessimisticSet = rs_reader = False = False = FalseEnd SubPrivate Sub Command2_Click()Dim rs_book As New Dim sql As Stringfindform = Falsesql = select * from 借閱信息 where 書籍編號=39。 amp。 amp。 39。 = adUseClient sql, conn, adOpenKeyset, adLockPessimisticSet = rs_book = False = False = FalseEnd SubPrivate Sub Command3_Click()Dim book_num As StringDim reader_num As StringDim answer As StringDim rs_back As New Dim sql As StringOn Error GoTo delerrorbook_num = (3).CellValue()reader_num = (1).CellValue()answer = MsgBox(確定要還這本書嗎？, vbYesNo, )If answer = vbYes Then sql = select * from 借閱信息 where 書籍編號=39。 amp。 book_num amp。 39。 = adUseClient sql, conn, adOpenKeyset, adLockPessimistic sql = select * from 書籍信息 where 書籍編號=39。 amp。 book_num amp。 39。 = adUseClient sql, conn, adOpenKeyset, adLockPessimistic (7) = 否 sql = select * from 讀者信息 where 讀者編號=39。 amp。 reader_num amp。 39。 = adUseClient sql, conn, adOpenKeyset, adLockPessimistic (8) = (8) 1 If findform = True Then Command1_Click Else Command2_Click End If MsgBox 成功刪除！, vbOKOnly + vbExclamation, = FalseElse Exit SubEnd Ifdelerror:If 0 Then MsgBox End IfEnd SubPrivate Sub Command4_Click()Unload MeEnd SubPrivate Sub Form_Load()Dim rs_reader As New Dim rs_book As New Dim sql As Stringsql = select * from 讀者信息 = adUseClient sql, conn, adOpenKeyset, adLockPessimisticIf Not Then Do While Not (1) (0) LoopEnd Ifsql = select * from 借閱信息 = adUseClient sql, conn, adOpenKeyset, adLockPessimisticIf Not Then Do While Not (3) (4) LoopEnd IfEnd Sub