Visual Basic数据库开发疑难问题解

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 & "/′úàíòμ??" & 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!