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#141: How save a file in BLOB and use 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/DBISAM/etc) and any file format (document of MS Word, spreadsheet of MS Excel, bitmap or jpeg pictures, wav-files etc)

Published: June 19, 2002

See also

	Viewer for TNEF-files (winmail.dat)
	DBISAM Password Recovery
	ABA Database Convert
	Clarion to Text converter
	Excel Reader (dll)
	SMMsg suite
	Paradox Viewer
	Fast Document Viewer
	ABA Document Convert
	Paradox ActiveX

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