Solved

Saving to BLOB field in dbExpress with a join

Posted on 2003-11-13
2
916 Views
Last Modified: 2008-01-16
Writing to and from Interbase BLOB fields in Delphi7 like this….

Memo.Text:=ClientDataset.FieldByName(‘NOTES’).AsString;
and
ClientDataset.FieldByName(‘NOTES’).AsString:=Memo.Text;

...works fine until the underlying dataset is a join and the fields need to be written explicitly to the joined tables by the providers BeforeUpdateRecord event.
Building SQL statements in this event from the fields to be updated works for non-blob field but doesn’t work for BLOB fields as there is no INSERT syntax allowable for BLOB fields.
The question is therefore what should the providers BeforeUpdateRecord event look like to handle this kind of field? Is it possible to do it this way or is there another way?
A solution involving the datasets provider is preferable as this nicely encapsulates updates to all affected tables.
0
Comment
Question by:RogerFroud
[X]
Welcome to Experts Exchange

Add your voice to the tech community where 5M+ people just like you are talking about what matters.

  • Help others & share knowledge
  • Earn cash & points
  • Learn & ask questions
2 Comments
 

Accepted Solution

by:
RogerFroud earned 0 total points
ID: 9782120
This solution seems to work ok but is a bit clumsy. Any better solution gets the points....

Dataset Provider BeforeUpdateRecord event
var
    SQL: String;
    myParams: TParams;
    FileStream : TFileStream; //debug only
    StringStream : TStringStream;
......
code to save all other fields using INSERT statements in SQL then....

      if (DeltaDS.FieldByName('NOTES').NewValue<>Null) then
        begin
          myParams := TParams.Create;
          myParams.Clear;
          myParams.CreateParam(ftBlob, 'BlobParam', ptInput);
          StringStream:=TStringStream.Create(DeltaDS.FieldByname('NOTES').NewValue);
          myParams.ParamByName('BlobParam').LoadFromStream(StringStream, ftBlob);
          StringStream.Free;
          SQL:=Format('UPDATE STOCKSUPPLIERS SET NOTES = :BlobParam WHERE STOCKSUPPLIERID = %d', [ID]);
          Connection.Execute(SQL, myParams);
          myParams.Free;
        end;
0

Featured Post

Free Tool: IP Lookup

Get more info about an IP address or domain name, such as organization, abuse contacts and geolocation.

One of a set of tools we are providing to everyone as a way of saying thank you for being a part of the community.

Question has a verified solution.

If you are experiencing a similar issue, please ask a related question

Introduction The parallel port is a very commonly known port, it was widely used to connect a printer to the PC, if you look at the back of your computer, for those who don't have newer computers, there will be a port with 25 pins and a small print…
In my programming career I have only very rarely run into situations where operator overloading would be of any use in my work.  Normally those situations involved math with either overly large numbers (hundreds of thousands of digits or accuracy re…
I've attached the XLSM Excel spreadsheet I used in the video and also text files containing the macros used below. https://filedb.experts-exchange.com/incoming/2017/03_w12/1151775/Permutations.txt https://filedb.experts-exchange.com/incoming/201…
Exchange organizations may use the Journaling Agent of the Transport Service to archive messages going through Exchange. However, if the Transport Service is integrated with some email content management application (such as an antispam), the admini…

733 members asked questions and received personalized solutions in the past 7 days.

Join the community of 500,000 technology professionals and ask your questions.

Join & Ask a Question