在VB中用ODBC API访问数据库

一、声明ODBC API函数

这些函数都在odbc32.dll中定义了，要在程序中调用这些函数，必须首先对它们进行声明。建立一个模块，在里面写入下列内容：

'== 声明odbc32.dll中定义的ODBC API函数 == Public Declare Function SQLAllocEnv Lib \Public Declare Function SQLAllocConnect Lib \As Integer Public Declare Function SQLAllocStmt Lib \Integer Public Declare Function SQLConnect Lib \szDSN$, ByVal cbDSN%, ByVal szUID$, ByVal cbUID%,ByVal szPWD$, ByVal cbPWD%) As Integer Public Declare Function SQLColAttributes Lib \icol%, ByVal fDescType%, ByVal rgbDesc As String,ByVal cbDescMax%, pcbDesc%, pfDesc&) As Integer Public Declare Function SQLDisconnect Lib \Public Declare Function SQLExecDirect Lib \szSqlStr$, ByVal cbSqStr&) As Integer Public Declare Function SQLFetch Lib \Public Declare Function SQLFreeConnect Lib \Integer Public Declare Function SQLFreeEnv Lib \Public Declare Function SQLFreeStmt Lib \fOption%) As Integer Public Declare Function SQLGetData Lib \ByVal fCType%, ByVal rgbValue As String,ByVal cbValueMax&, pcbValue%) As Integer Public Declare Function SQLNumResultCols Lib \pccol%) As Integer Public Declare Function SQLGetDiagRec Lib \ByVal Handle&, ByVal RecNumber%, Sqlstate%,NativeErrorPtr%, MessageText As String, ByVal Bufferlenchgth%,TextlenchgthPtr%) 数据库访问常量和数据源信息常量：

'数据库访问常量 Public Const SQL_C_CHAR As Long = 1 Public Const SQL_COLUMN_LABEL As Long = 18 Public Const SQL_DROP As Long = 1 Public Const SQL_DRROR As Long = -1 Public Const SQL_NO_DATA_FOUND As Long = 100 Public Const SQL_SUCCESS As Long = 0 Public Const SQL_SUCCESS_WITH_INFO As Long = 1 Public Const SQL_ATTR_MAX_LENGTH As Long = 100 '数据源信息常量 Public Const DATABASE As String = \Public Const DSN As String = \Public Const DB_USER_NAME As String = \Public Const DB_PASSWORD As String = \'版本号 Public Const VerNum As String = \版本 1.0.01\'生成日期 Public Const GenDate As String = \日期 2002-08-26\'一次执行connect操作可以访问数据库的次数 Public Const CONNECT_LOOP_MAX = 10

二、初始化ODBC

'== 标记数据库是否连接 == Private IsConnect As Boolean '== 标记执行Connect()函数后，访问数据库的次数 == Private Connect_Num As Integer Private Henv AsLong '环境句柄 Private Hdbc AsLong '连接句柄 Private Rc As Long Public Hstmt As Long

三、与ODBC数据库建立连接

'连接数据库 Private Sub Connect() Dim TmpStat As Long 'SQLConnect()函数的返回值 '如果连接标记为真，则返回。否则会出错 If IsConnect = True Then ExitSub End If '分配环境句柄，保存在变量Henv中 If SQLAllocEnv(Henv) Then MsgBox\无法初始化ODBC环境!\执行错误\ End End If '根据环境句柄，分配连接句柄，保存在变量Hdbc中 If SQLAllocConnect(Henv, Hdbc) Then MsgBox\无法连接ODBC!\执行错误\ End End If '根据连接句柄、数据源、用户名和密码连接指定的数据库 TmpStat = SQLConnect(Hdbc, DSN, Len(DSN),DB_USER_NAME, _ Lench(DB_USER_NAME), DB_PASSWORD, Len(DB_PASSWORD)) '如果连接不成功则退出程序 If TmpStat <> SQL_SUCCESS And _ TmpStat <> SQL_SUCCESS_WITH_INFO Then MsgBox\无法获得连接句柄!\执行错误\ IsConnect =True Disconnect End End If '设置连接标记 IsConnect = True End Sub '使用Connect_Num控制数据库连接 Public Sub DB_Connect() Connect_Num = Connect_Num + 1 Connect End Sub

四、存储数据

'执行ODBC数据库操作语句 Public Sub OdbcExt(ByVal TmpSQLstmt As String) '根据连接句柄，分配语句句柄 If SQLAllocStmt(Hdbc, Hstmt) Then MsgBox\句柄分配失败\执行错误\ DBapi_Disconnect End End If '执行SQL语句，Lench是用户自定义函数，计算包含汉字的字符串长度 If SQLExecDirect(Hstmt, TmpSQLstmt,Lench(TmpSQLstmt)) Then MsgBox\数据库访问语句执行失败\执行错误\ MsgBoxTmpSQLstmt DBapi_Disconnect End End If End Sub '使用Data控件连接数据库，将执行指定的SQL语句 Public Sub DBdataExt(TmpData As Data, ByVal TmpSource AsString) '关闭已有的ODBC连接 DBapi_Disconnect 'Data控件连接数据库 TmpData.Connect = \ + \ + DB_PASSWORD + \ TmpData.RecordSource = TmpSource TmpData.Refresh End Sub

五、结束应用程序

'断开与数据库的连接 Private Sub Disconnect() Dim Rc As Long '如果连接标记为假，标明已经断开连接，则直接返回 If IsConnect = False Then ExitSub End If '断开连接 Rc = SQLDisconnect(Hdbc) '释放连接句柄 Rc = SQLFreeConnect(Hdbc) '释放环境句柄 Rc = SQLFreeEnv(Henv) IsConnect = False End Sub Public Sub DB_Disconnect() If Connect_Num >= CONNECT_LOOP_MAX Then Connect_Num= 0 Disconnect End If End Sub '强制关闭api方式访问的数据库，计数器复位 Public Sub DBapi_Disconnect() Connect_Num = 0 Disconnect End Sub