bug re TSQLQuery?
lazarus / 16-Databases

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peppepolpo · 2020-11-29 21:16

I am a long time user of Delphi and a beginner in Lazarus.

Currently I am using Lazarus 1.8.4 in Windows7.

I found a weird behaviour of component TSQLQuery.

It seems a bug to me, but I would like to discuss the question here.

say you have
qry:TSQLQuery;
IBConnection:TIBConnection;
trRead:TSQLTransaction;

I use these components to access a Firebird v. 2.5 DB.

I wrote the code below (please read the code at the bottom of this
message).

When the program reaches the last line
   a:=qry.FieldByName('id_cst').IsNull;

an exception is raised saying 'field ID_CST not found'.

It took a while to me to realize that I assigned the query SQL in
   qry.SQL.Text:='select * from tb_cst';

without closing the query first. The correct code would be:

   qry.Close;
   qry.SQL.Text:='select * from tb_cst';

However Delphi does not allow to assign the SQL of an open query and
the exception would have been raised in this line
   qry.SQL.Text:='select * from tb_cst';

What Delphi does seems the correct way to go. At least, I would have
spared a long time trying to understand the problem.

Should I report a bug? Or maybe this behaviour has been corrected in
the most recent versions?

Thank you

Peppe Polpo


var
   a:boolean;
begin

   // access the DB
   try
      IBConnection.Connected:=true;
   except
      ShowMessage('Cannot connect to the server');
      Close;
      Exit;
   end;

   qry.Close;
   qry.SQL.Text:='select * from tb_dpt';
   (*
   structure is
   CREATE TABLE TB_DPT (
   ID_DPT                 CHAR( 36 )             NOT NULL,
   COD_DPT                VARCHAR( 13 )          NOT NULL,
   PRIMARY KEY ( ID_DPT )
   )
   *)


   qry.Open;
   qry.First;
   a:=qry.FieldByName('id_dpt').IsNull; // check for field ID_DPT: OK

   qry.SQL.Text:='select * from tb_cst';
   (*
   structure is
   CREATE TABLE TB_CST (
   ID_CST                 CHAR( 36 )             NOT NULL,
   COD_CST                VARCHAR( 13 )          NOT NULL,
   PRIMARY KEY ( ID_CST )
   )
   *)


   qry.Open;
   qry.First;
   a:=qry.FieldByName('id_cst').IsNull; // check for field ID_CST: an
exception is raised here







I use