how exactly read blob field
lazarus / 16-Databases

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deepblue · 2009-08-24 11:52

i have a table with blob field..this field is for picture.
i have try to SQLdb and TDBImage component but it doesn't work.
my step is:
1. add SQLConnector. I set Connected to true and no error
2. add SQLQuery1. I set SQL with 'select * from product order by
code'. and active property to true. no error
3. i double click in SQLQuery. I do Add Fields in 'Edit Fields -
SQLQuery1'..i add 'picture' field as TBlobField.

the problem is:
i choose that tblobfield
and i saw strange Blobtype property (under Alignment in Object
Inspector)..
that property's combobox shows: three empty space,??,??,{,Dataset,ef4V
?,ftFixedWideChar,ftFMTBcd,ftGuid,ftIDispacth,ftInterface,ftOraBlob,ft
OraClob,ftTimeStamp,ftvariant,ftWideMemo,TdatasetNotifyEvent.

CMIIW, it should be 'TBlobType = ftBlob..ftWideMemo;' (i saw in db.pas
line 791)

is there a bug in FPC or LCL?

i tried to set SQLQuery1picture.BlobType:=ftGraphic; in form create
procedure but it's doesn't show picture in tdbimage..

NB:I have same condition with Zeos

please help me..
thanks..

My Lazarus Version:Lazarus 0.9.29 r21262:21406M FPC 2.3.1
i386-win32-win32/win64

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Loesje · 2009-08-25 16:19

The format of the data in the blob-field has to be recognized by
TDBImage. Try to add a picture in TDBImage, then write it to the
database and then open it again. That way you know for sure that the
format is ok. (Just binary data with a .gif or something won't work.
It needs a header with the image-type)

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halityilmaz · 2010-08-25 08:39

this is not aout your question, i know and i am sorry but i want to
ask you what you used for ConnectorType Property of SqlConnector?

I have ( unknown connector type) error every time when i want to
connect to the sql server.

thank you.

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guidoaerts · 2010-08-27 07:08

this is an example:

var
fstream : tStream;
fgraph : tjpegimage;   
begin
 if not (tblobfield(fieldbyname('foto')).IsNull) then
     begin
        fstream :=
gquery.CreateBlobStream(gquery.FieldByName('foto'),bmread);
        fgraph := tjpegimage.create;
        try
          fgraph.LoadFromStream(fstream);
          fotoimage.Picture.Assign(fgraph);
        finally
          fstream.free;
          fgraph.free;
        end;
     end;              
end;

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Lacak2 · 2010-08-31 05:43

Quote from: halityilmaz on August 25, 2010, 10:39:28 amthis is not
aout your question, i know and i am sorry but i want to ask you what
you used for ConnectorType Property of SqlConnector?

I have ( unknown connector type) error every time when i want to
connect to the sql server.

It depends on type of SQL Server you are connecting to. For example:
ODBC: 'ODBC'
Oracle: 'Oracle'
MySQL: 'MySQL 4.1', 'MySQL 5.0'
Interbase, Firebird: 'Firebird'
etc.

But you can use instead of SQLConnector some of individual
SQLConnections (TODBCConnection,TOracleConnection,...) objects when
you know to which SQL Server you want connect to.