oracle中可用LOB 字段來存儲長文本或者二進(jìn)制數(shù)據(jù)，LOB分為BLOB合CLOB，其中BLOB可用來存儲二進(jìn)制數(shù)據(jù)，如exe、dll、視頻、音頻等；CLOB只能用來存儲字符型文本數(shù)據(jù)。
舉個(gè)VB存取BLOB字段的簡單例子，首先在oracle中建一有BLOB字段的表
SQL:
create table TEST_TABLE(id number(4) not null,fileName varchar2(255),fileContent BLOB)
在VB中寫代碼:
Dim cnn As New ADODB.Connection '全局?jǐn)?shù)據(jù)
Dim rs1 As New ADODB.Recordset '全局?jǐn)?shù)據(jù)
Dim SQL As String '全局?jǐn)?shù)據(jù)
Private Sub Command1_Click()
SaveFile ("D:\7.JPG")
End Sub
Private Sub Command2_Click()
GetFile
End Sub
Private Sub Form_Load()
cnn.ConnectionString = "Provider=OraOledb.Oracle.1;" _
& "Password=mygps;" _
& "User ID=usermygps;" _
& "Data Source=mygps@mygps;" _
& "Persist Security Info=True"
cnn.Open '打開數(shù)據(jù)庫連接
End Sub
'－－－－－－－－－－－－－插入一條記錄，存儲文件數(shù)據(jù)－－－－－－－－－－－－－－－－－
Private Sub SaveFile(strFileName As String)
rs1.LockType = adLockOptimistic
rs1.CursorLocation = adUseClient
rs1.Open "TEST_TABLE", cnn, adCmdTable
rs1.AddNew
rs1.Fields("id").Value = 1
rs1.Fields("fileName").Value = strFileName
Call FileToBlob(rs1.Fields("fileContent"), strFileName)
rs1.Update
rs1.Close
Set rs1 = Nothing
End Sub
'－－－－－－－－－－－－－讀取一條記錄，獲取文件數(shù)據(jù)，并寫入文件－－－－－－－－－－－
Private Sub GetFile()
strSql = "select * from TEST_TABLE where id='2'"
Debug.Print strSql
rs1.LockType = adLockOptimistic
rs1.CursorLocation = adUseClient
rs1.Open strSql, cnn, adOpenKeyset
If rs1.RecordCount > 0 Then
BlobToFile rs1.Fields("fileContent"), rs1.Fields("fileName").Value, rs1.Fields("fileContent").ActualSize
End If
rs1.Close
Set rs1 = Nothing
End Sub
'－－－－－－－－－－－－－文件數(shù)據(jù)轉(zhuǎn)BLOB－－－－－－－－－－－－－－－－－－－－－－
Private Sub FileToBlob(fld As ADODB.field, FileName As String, Optional ChunkSize As Long = 8192)
Dim fnum As Integer, bytesLeft As Long, bytes As Long
Dim tmp() As Byte
If (fld.Attributes And adFldLong) = 0 Then
Err.Raise 1001, , "Field doesn't support the GetChunk method."
End If
fnum = FreeFile
Open FileName For Binary As fnum
bytesLeft = LOF(fnum)
Do While bytesLeft
bytes = bytesLeft
If bytes > ChunkSize Then bytes = ChunkSize
ReDim tmp(1 To bytes) As Byte
Get #1, , tmp
fld.AppendChunk tmp
bytesLeft = bytesLeft - bytes
Loop
Close #fnum
End Sub
'－－－－－－－－－－－－－BLOB數(shù)據(jù)轉(zhuǎn)存文件－－－－－－－－－－－－－－－－－－－－－
Private Sub BlobToFile(fld As ADODB.field, FileName As String, Optional ChunkSize As Long)
Dim fnum As Integer, bytesLeft As Long, bytes As Long
Dim tmp() As Byte
If (fld.Attributes And adFldLong) = 0 Then
Err.Raise 1001, , "Field doesn't support the GetChunk method."
End If
If Dir$(FileName) <> "" Then Kill FileName
fnum = FreeFile
Open FileName For Binary As fnum
bytesLeft = fld.ActualSize
Do While bytesLeft
bytes = bytesLeft
If bytes > ChunkSize Then bytes = ChunkSize
tmp = fld.GetChunk(bytes)
Put #fnum, , tmp
bytesLeft = bytesLeft - bytes
Loop
Close #fnum
End Sub
