changes on the form not in the database
lazarus / 16-Databases

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Kristen · 2014-06-19 19:07

Hello,

I'm a newbie trying to learn about Lazarus and databases. A small
example prog I found on the net works allright, except that changes
made on the form when the prog is running don't alter the tables in
the data base.

I use 1  TDataSource, 1 TDBGrid, 1 TDBNavigator, 1  MySQL55Connection,
1  TSQLQuery & 1 TSQLTransaction.

I've got this too :

procedure TForm1.SQLQuery1AfterDelete(DataSet: TDataSet);
begin
  SQLQuery1.ApplyUpdates ();
end;

procedure TForm1.SQLQuery1AfterPost(DataSet: TDataSet);
begin
    SQLQuery1.ApplyUpdates ();
end;  

It _seems _ to work allright  when I use the navigator for deleting,
adding or editing, but if I close and reopen the program, nothing has
changed. I've got a warning concerning TDataset not being used when
compiling, but I don't know what else Ishould pass to the AfterDelete
or AfterPost procs.

Thanks for reading !

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Mike.Cornflake · 2014-06-19 19:37

Something changed somewhere recently.  Changes to a DB all occur in a
Transaction.  I'll be honest, I normally work in read only databases,
so I'm vague on the whole transaction thingy - particularly as they
apply to SQLDB, but I suspect that if you add a TSQLTransation.Commit
somewhere in your code you'll be fine.

From what I do know of transactions, I consider them a necessary
evil.  I'd put your .Commit as early as you possibly can.  I don't
know about MySQL, but MS SQL will lock any table for other users if
it's used in a transaction.

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Kristen · 2014-06-19 19:52

Thanks a million, Mike !

That was a quick one ! You put me on the right track : I changed the
TSQLTransaction's action property from caRollback to caCommit and that
was it !

Thanks again