vb 保存图片到数据库

VBA读写BLOB字段

最新推荐文章于 2021-02-22 06:23:28 发布

原创最新推荐文章于 2021-02-22 06:23:28 发布 · 675 阅读

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#vb #integer #access #string #byte #数据库

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本文介绍使用VBA在数据库中读取和写入二进制大对象(BLOB)字段的方法。通过两个子程序实现：一是从BLOB字段读取数据到文件，二是将文件数据保存到BLOB字段中。此技术适用于处理图像、音频等多媒体数据。

'读数据到二进制字段
Public Sub ReadFromBLOB(filed As ADODB.Field, Filen As String)

Dim DataFile As Integer, Fl As Long, Chunks As Integer
Dim Fragment As Integer, Chunk() As Byte, i As Integer
'传送块单位大小
Const ChunkSize As Integer = 16384

Dim MediaTemp As String
Dim lngOffset As Long
Dim lngTotalSize As Long
Dim strChunk As String
Dim MediaID As Long
On Error Resume Next

DataFile = FreeFile

Open Filen For Binary Access Write As DataFile

lngTotalSize = filed.ActualSize
Chunks = lngTotalSize / ChunkSize
Fragment = lngTotalSize Mod ChunkSize

'ReDim Chunk(ChunkSize)
ReDim Chunk(Fragment)

Chunk() = filed.GetChunk(ChunkSize)
Put DataFile, , Chunk()
lngOffset = lngOffset + ChunkSize
Do While lngOffset < lngTotalSize
   Chunk() = filed.GetChunk(ChunkSize)
   Put DataFile, , Chunk()
   lngOffset = lngOffset + ChunkSize
Loop
Close DataFile

End Sub
'写数据到二进制字段
Public Sub SaveToBLOB(fieldBLOB As ADODB.Field, filename As String)
Dim DataFile As Integer, Fl As Long, Chunks As Integer
Dim Fragment As Integer, Chunk() As Byte, i As Integer
'传送块单位大小
Const ChunkSize As Integer = 16384

Dim MediaTemp As String
Dim lngOffset As Long
Dim lngTotalSize As Long
Dim strChunk As String
Dim MediaID As Long

DataFile = FreeFile

Open filename For Binary Access Read As DataFile
    Fl = LOF(DataFile)    ' 文件中数据长度
    If Fl = 0 Then
       Close DataFile
    Else
    Chunks = Fl / ChunkSize
    Fragment = Fl Mod ChunkSize
    'If Chunks <= 0 Then Chunks = 1
    ReDim Chunk(Fragment)
    Get DataFile, , Chunk()
    fieldBLOB.AppendChunk Chunk()
    ReDim Chunk(ChunkSize)

    For i = 1 To Chunks
     Get DataFile, , Chunk()
     fieldBLOB.AppendChunk Chunk()
    Next i
    Close DataFile
   End If

End Sub