[DUG] Blob primer

[Phil Middlemiss]

Very useful, thankyou.

Phil.

Robert martin wrote:

> Hi.
>
> Dont know if this helps but here is how we load and seve data (cut 
> from code messily).  We are using IBO and Firebird.
>
>    with zMainDM.GeneralIB_Query do begin
>        IB_Transaction.StartTransaction;
>        try
>            SQL.Text := 'SELECT r.FileName, ra.FileBlob ' +
>                        'FROM ReportActivity ra ' +
>                        'JOIN Report r ON r.ReportRef = ra.ReportRef ' +
>                        'WHERE ra.ActivityRef = :ActivityRef;';
>            Prepare;
>
>                            //Extract Archived file
>                            FileStream := TFileStream.Create(FileName + 
> 't', fmCreate);
>                            try
>                                DBStream := 
> CreateBlobStream(FieldByName('FileBlob'), bsmRead);
>                                try
>                                    FileStream.CopyFrom(DBStream, 0);
>                                finally
>                                    DBStream.Free;
>                                end;
>                            finally
>                                FileStream.Free;
>                            end;
> ...
>
> //The above runs an SQL to select the desire blob and saves it to a 
> file (with an extra 't' in the name for obscure reasons :) )
>
>
>
>
>
>
>                    zMainDM.InsertActivityIB_Query.SQL.Text := 'INSERT 
> INTO ReportActivity ' +
>                                                                
> '(ActivityRef, ReportRef, VersionNo, rDate, rTime, Comment, UserRef, 
> Activity, FileBlob, Approved, Canceled) ' +
>                                                                'VALUES 
> ' +
>                                                                
> '(:ActivityRef, :ReportRef, :VersionNo, :rDate, :rTime, :Comment, 
> :UserRef, :Activity, :FileBlob, :Approved, ''F'');';
>                    zMainDM.InsertActivityIB_Query.Prepare;
>
> .....
>
>                //Compress Report and insert into query
>                CompLHA.ForceUpperCase := False;
>                CompLHA.FilesToProcess.Clear;
>                CompLHA.FilesToProcess.Add(InEdit.Text);
>                CompLHA.ArchiveName := ExtractFileName(InEdit.Text);
>                CompLHA.CompressionMethod := colh5;
>
>                SList   := TStringList.Create;
>                Stream  := TMemoryStream.Create;
>                try
>                    SList.Add(InEdit.Text);
>
>                    CompLHA.CompressFilesToStream(Stream, SList, colh5);
>
>                    //Stream now contains compressed file, copy to 
> insert statement
>                    DBStream := 
> zMainDM.InsertActivityIB_Query.CreateBlobStream(zMainDM.InsertActivityIB_Query.ParamByName('FileBlob'), 
> bsmWrite);
>
>                    DBStream.CopyFrom(Stream, 0);
>                finally
>                    Stream.Free;
>                    SList.Free;
>                end;
>
>
> The above has an insert SQL to load the blob.  It compresses the file 
> and loads it into the query to insert.  You could replace the CompLHA 
> stuff with a std stream load.
>
>
>
> It is really quite simple to use, just a mix of SQL and TStreams.
>
>
>
> Rob Martin
> Software Engineer
>
> phone +64 03 377 0495
> fax   +64 03 377 0496
> web www.chreos.com
>
> Wild Software Ltd
>
>
>
> Phil Middlemiss wrote:
>
>> Could anyone give me a link to a "how-to" about blobs? I'm using D6 
>> with firebird - there is no GUI (it's a service) so I would like to 
>> just use SQL if possible.
>>
>> Having not used blobs before I'm wondering:
>> - what is a subtype? The Interbase documentation assumes you know
>> - what is a good size for the segment length
>> - how to specify binary data in a sql - if it's actually possible.
>> - if I can't just use sql then what's the best way?
>>
>> Phil.
>>
>> _______________________________________________
>> Delphi mailing list
>> Delphi at ns3.123.co.nz
>> http://ns3.123.co.nz/mailman/listinfo/delphi
>>
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>
>
>