Visual Basic数据库开发疑难问题解

我始终认为Visual Basic是数据库开发最便捷的工具，我在论坛中看到不少朋友提出的关于VB数据库开发方面的问题，有许多问题是反复提出，也有些我认为是比较典型的问题，我将这些问题收录在一起同时提出答案，便于网友们查阅，如果你还有社呢们提可以给我写信。

　　问：如何显示格式为03-3-13的日期？

　　解决的方法：

1　 Cmd.CommandText = "select * from 支出 where 日期=03-3-13" 中 03-3-13=-13。 日期实际上是Double型数字。0 是 1899-12-30，-13 是 1899-12-17。你当然没有这样日期的记录，所以只有大于才行。 2 Cmd.CommandText = "select * from 支出 where 日期=#03-3-13#" 凡是没有明示，文字型日期是按美国习惯解释的，#03-3-13# 是 0013-03-03。 或者使用长日期格式： Cmd.CommandText = "select * from 支出 where 日期=#2003-3-13#" 用格式化函数： Cmd.CommandText = "select * from 支出 where 日期=#" & format(mydate,"yyyy-mm-dd") & "#"

　　问： 如何判断DNS是否存在？怎样才能列举出所有的DNS?

　　解决方法：

1、通过利用ODBC API中的SQLDataSource函数可以取得ODBC API中数据源的列表。 判断DNS是否存在： 　 　　2、使用API函数Private Declare Function SQLDataSources Lib "ODBC32.DLL" (ByVal henv As Long, ByVal fDirection As Integer, ByVal szDSN As String, ByVal cbDSNMax As Integer, pcbDSN As Integer, ByVal szDescription As String, ByVal cbDescriptionMax As Integer, pcbDescription As Integer) As Integer Private Declare Function SQLAllocEnv Lib "ODBC32.DLL" (ByRef env As Long) As Long 列举出所有DNS。

　　问：处理文本文件是导入数据库还是直接读写文件呢？

　　解决方法：

Set main = bumony.OpenRecordset("main") Open App.Path & "\sources\" & Text1.Text & "\´úÀíÒµÎñ" & Text1.Text & ".txt" For Input As #1 Do While Not EOF(1) Line Input #1, str1 With main .AddNew !code = Mid(str1, 1, 5) !date = Text1.Text If Mid(str1, 1, 5) = "21310" Or Mid(str1, 1, 5) = "21311" Or Mid(str1, 1, 5) = "21410" Or Mid(str1, 1, 5) = "21411" Then !Money = Trim(Mid(str1, 7, 10)) Else !Money = Trim(Mid(str1, 7, 10)) & "0000" End If !whao = "1102" !ywhao = "1102" .Update End With Loop Close #1 main.Close

　　问：调用SQL存储后有参数返回,应该怎么赋值?

　　解决方法：

Dim ADOCmd As New ADODB.Command Dim ADOPrm As New ADODB.Parameter Dim ADORs As ADODB.Recordset '.... Set ADOCmd.ActiveConnection = ADOCon With ADOCmd .CommandType = adCmdStoredProc .CommandText = "ADOTestRPE" End With sParmName = "Output" Set ADOPrm = ADOCmd.CreateParameter(sParmName, adInteger, adParamOutput) ADOCmd.Parameters.Append ADOPrm ADOCmd.Parameters(sParmName).Value = 999 Set ADORs = ADOCmd.Execute '..... Debug.Print "Output: " & ADOCmd.Parameters("Output").Value

　　问： SQL Server 2000中如何存取图片信息？
　　
　　解决方法:

新建一个工程,添加 ado 控件,2个 Command ,1个 Picture,1个 Image Dim Chunk() As Byte Dim lngLengh As Long Dim intChunks As Integer Dim intFragment As Integer Const ChunkSize = 1000 Const lngDataFile = 1 Private Sub cmdBrowse_Click() On Error Resume Next With cmdlFilePath .Filter = "JPG Files|*.JPG|Bitmaps|*.BMP" .ShowOpen txtFilePath.Text = .filename End With End Sub Private Sub Savepic() Open "c:\colordraw0094_m.jpg" For Binary Access Read As lngDataFile lngLengh = LOF(lngDataFile) If lngLengh = 0 Then Close lngDatafile: Exit Sub intChunks = lngLengh \ ChunkSize intFragment = lngLengh Mod ChunkSize 'OpenData 打开数据库 Dim i As Integer Dim rs As New ADODB.Recordset Dim strQ As String If rs.State = adStateOpen Then rs.Close strQ = "Select * From [mydata]" rs.Open strQ, conn, adOpenStatic, adLockOptimistic On Error Resume Next rs.AddNew ReDim Chunk(intFragment) Get lngDataFile, , Chunk() rs.Fields("rs_photo1").AppendChunk Chunk() ReDim Chunk(ChunkSize) For i = 1 To intChunks Get lngDataFile, , Chunk() rs.Fields("rs_photo1").AppendChunk Chunk() Next i rs.Update rs.Close Close lngDataFile Call ShowPic End Sub Public Sub ShowPic() 'OpenData 打开数据库 Dim i As Integer Dim rs As New ADODB.Recordset Dim strQ, filename As String If rs.State = adStateOpen Then rs.Close strQ = "Select * From [mydata]" rs.Open strQ, conn, adOpenStatic, adLockOptimistic If rs.EOF <> True Then rs.MoveLast Else Exit Sub End If On Error Resume Next Open "pictemp" For Binary Access Write As lngDataFile lngLengh = rs.Fields("rs_photo1").ActualSize intChunks = lngLengh \ ChunkSize intFragment = lngLengh Mod ChunkSize ReDim Chunk(intFragment) Chunk() = rs.Fields("rs_photo1").GetChunk(intFragment) Put lngDataFile, , Chunk() For i = 1 To intChunks ReDim Buffer(ChunkSize) Chunk() = rs.Fields("rs_photo1").GetChunk(ChunkSize) Put lngDataFile, , Chunk() Next i Close lngDataFile filename = "pictemp" Picture1.Picture = LoadPicture(filename) Image1.Stretch = True Image1.Picture = Picture1.Picture Kill filename End Sub Private Sub Command1_Click() Savepic End Sub Private Sub Command2_Click() ShowPic End Sub 上面写的是acess的代码!楼主可以改一下连接数据库的设置代码用于sql server!