How to save some file in BLOB-field and use it later

If you develop a database related software, then very popular task is to
save some files (documents/images/reports/etc) in some BLOB field of table
and use these saved data later.

In this tip I want to show how this task could be solved.

To save a file to BLOB:
blob := yourDataset.CreateBlobStream(yourDataset.FieldByName('YOUR_BLOB'),
bmWrite);
try
  blob.Seek(0, soFromBeginning);

  fs := TFileStream.Create('c:\your_name.doc', fmOpenRead or
fmShareDenyWrite);
  try
    blob.CopyFrom(fs, fs.Size)
  finally
    fs.Free
  end;
finally
  blob.Free
end;

To load from BLOB:
blob := yourDataset.CreateBlobStream(yourDataset.FieldByName('YOUR_BLOB'),
bmRead);
try
  blob.Seek(0, soFromBeginning);

  with TFileStream.Create('c:\your_name.doc', fmCreate) do
    try
      CopyFrom(blob, blob.Size)
    finally
      Free
    end;
finally
  blob.Free
end;

Using this code you can work with any database engine (BDE/ADO/DAO/ODBC/etc)
and any file format (document of MS Word, spreadsheet of MS Excel, bitmap or
jpeg pictures, wav-files etc)

With best regards, Mike Shkolnik
E-Mail: mshkolnik@scalabium.com
WEB: http://www.scalabium.com