Is it possible to return an array of bytes from a SQL Server VarBinary column using a parameterized query?

Question

I wrote a small VBA procedure to check the upload and download of files as binary data in and out of a VarBinary column in SQL Server using ADO. The boot process seems to work, but I can't get the boot process to work.

I believe that the output parameter for VarBinary is set incorrectly, but I can not find the documentation on how to do this correctly.

I get a runtime error 3708 "The parameter object is incorrectly defined. Inconsistent or incomplete information provided." on the line.Parameters.Append .CreateParameter("@myblob", adVarBinary, adParamOutput)

Update: SELECT ? = myblob FROM bin_table WHERE ID = ?;appears as returning a binary string, not a binary array. I think this is the problem, but I still don't know how to fix it.

Update: I fixed the compilation error "Type mismatch: array or custom type expected" by adding an append .Valueto the end of the line WriteFile "C:\some_new_file.pdf", .Parameters("@myblob").

Any help is appreciated. Thank!

Private Sub TestReadWriteBlob()

    Dim objConnection As New ADODB.Connection
    Dim objCommand As New ADODB.Command
    Dim objRecordset As New ADODB.Recordset
    Dim intNewID As Integer

    With objConnection
        .CursorLocation = adUseClient
        .ConnectionString = "PROVIDER=SQLOLEDB;Server=<server>;Database=<database>;UID=<uid>;PWD=<pwd>;trusted_connection=false;"
        .Open
    End With

    With objCommand
        .ActiveConnection = objConnection
        .CommandText = "INSERT INTO bin_table ( myblob ) VALUES ( ? ); SELECT ? = id FROM bin_table WHERE ID = @@IDENTITY;"
        .CommandType = adCmdText
        .Parameters.Append .CreateParameter("@myblob", adVarBinary, adParamInput, -1, ReadFile("C:\some_file.pdf"))
        .Parameters.Append .CreateParameter("@NewID", adInteger, adParamOutput)
        .Execute
        intNewID = .Parameters("@NewID")
    End With

    Debug.Print intNewID

    Set objCommand = Nothing
    With objCommand
        .ActiveConnection = objConnection
        .CommandText = "SELECT ? = myblob FROM bin_table WHERE ID = ?;"
        .CommandType = adCmdText
        .Parameters.Append .CreateParameter("@myblob", adVarBinary, adParamOutput)
        .Parameters.Append .CreateParameter("@NewID", adInteger, adParamInput, , intNewID)
        .Execute
        WriteFile "C:\some_new_file.pdf", .Parameters("@myblob").Value
    End With

End Sub

Public Function ReadFile(ByVal strPath As String) As Byte()

    Dim intFile As Integer

    intFile = FreeFile
    Open strPath For Binary Access Read As intFile
    ReDim ReadFile(LOF(intFile) - 1)
    Get intFile, , ReadFile
    Close intFile

End Function

Public Sub WriteFile(ByVal strPath As String, bytBlob() As Byte, Optional ByVal Overwrite As Boolean = True)

    Dim intFile As Integer

    intFile = FreeFile
    If Overwrite And Dir(strPath) <> "" Then
        Kill strPath
    End If
    Open strPath For Binary Access Write As intFile
    Put intFile, , bytBlob
    Close intFile

End Sub

Answer 1

I could not find a way to return an array of bytes from a VarBinary column in SQL Server using a parameter. However, I found out that this is done from the records. Nested code does the job.

- , - .

Private Sub TestReadWriteBlob()

    Dim objConnection As New ADODB.Connection
    Dim objCommand As New ADODB.Command
    Dim intNewID As Integer

    With objConnection
        .CursorLocation = adUseClient
        .ConnectionString = "PROVIDER=SQLOLEDB;Server=<server>;Database=<database>;UID=<uid>;PWD=<pwd>;trusted_connection=false;"
        .Open
    End With

    With objCommand
        .ActiveConnection = objConnection
        .CommandText = "INSERT INTO bin_table ( myblob ) VALUES ( ? ); SELECT ? = id FROM bin_table WHERE ID = @@IDENTITY;"
        .CommandType = adCmdText
        .Parameters.Append .CreateParameter("@myblob", adVarBinary, adParamInput, -1, ReadFile("C:\Users\Thomas\Desktop\some_file.pdf"))
        .Parameters.Append .CreateParameter("@NewID", adInteger, adParamOutput)
        .Execute
        intNewID = .Parameters("@NewID")
    End With

    Set objCommand = Nothing
    With objCommand
        .ActiveConnection = objConnection
        .CommandText = "SELECT myblob FROM bin_table WHERE ID = ?;"
        .CommandType = adCmdText
        .Parameters.Append .CreateParameter("@NewID", adInteger, adParamInput, , intNewID)
        WriteFile "C:\Users\Thomas\Desktop\blob\some_file.pdf", .Execute.Fields("myblob").Value
    End With

End Sub

Public Function ReadFile(ByVal strPath As String) As Byte()

    Dim intFile As Integer

    intFile = FreeFile
    Open strPath For Binary Access Read As intFile
    ReDim ReadFile(LOF(intFile) - 1)
    Get intFile, , ReadFile
    Close intFile

End Function

Public Sub WriteFile(ByVal strPath As String, bytBlob() As Byte, Optional ByVal Overwrite As Boolean = True)

    Dim intFile As Integer

    intFile = FreeFile
    If Overwrite And Dir(strPath) <> "" Then
        Kill strPath
    End If
    Open strPath For Binary Access Write As intFile
    Put intFile, , bytBlob
    Close intFile

End Sub