What makes a dataset read-only?

[AKCarlow]

I have two separate dbGrids on a form, each populated by its own SQLQuery, each showing data from different tables in the same local MySQL 5 database. On one of them I can edit a cell by clicking on it; when I ApplyUpdates the changes are written to the database.

On the other clicking a cell does highlight it, but I cannot edit it. One of the columns is for a TinyInt (boolean) field and is correctly showing as checkboxes. I have an OnClick handler for this grid - if I click anywhere in the grid, I get the pirate 1 message, and if I click in the Estimate (TinyInt) column I get pirate 1 and 2, but not 3, and the program crashes with a "dataset is read-only" error. As far as I can see, the settings for things like Active and Enabled on the various components are the same in both cases. What am I doing wrong? 

Code: [Select]

procedure TfShareReg.dbgUsageCellClick(Column: TColumn);
begin
ShowMessage('pirate 1');
If Column.FieldName = 'Estimate' then
  begin
  ShowMessage('pirate 2');
  qUsage.Active:=true;
  qUsage.Edit;
  ShowMessage('pirate 3');
  if Column.Field.OldValue = 0 then
     begin //do estimate
     showmessage('make an estimate');
     Column.Field.NewValue := 1;
     end {do estimate}
  else
      begin {undo estimate}
      showmessage('put it back');
      Column.Field.Value:=0;
      end; {undo estimate}
  qUsage.ApplyUpdates;
  end;
end;     


[BigChimp]

Do the insertsql, deletesql and updatedsql properties contain the relevant SQL? If not (e.g. when you have a more complicated query than a simple select), you'll have to fill those properties yourself...

[AKCarlow]

In both cases InsertSQL etc are empty, but ParseSQL is true. Both cases have a parameterised WHERE clause - the parameter is set by a DataChange event handler in another data set eg

Code: [Select]

  qUsage.Close;
  qUsage.Params.ParamByName('paramShare').AsString:=dbtxtShareNo.Caption;
  qUsage.Open;

Both grids properly show the expected values for the selected row in the other dataset.

[LacaK]

What is in qUsage.SQL.Text ?

[AKCarlow]

select ShareNo,ReadingDate,Connection,Reading,Previous,Note,Estimate,Actual, Reading-Previous as M3Used from Connections join MeterReadings on ConnectionNo = Connection where ShareNo = :paramShare order by Connection,ReadingDate desc;       

[LacaK]

Then it is expected behavior, that dataset is ReadOnly.
If SQL is multi-table select (better say something else than single table select), then you must supply own InsertSQL, UpdateSQL, DeleteSQL to let sqlDB know which tables to update.

[AKCarlow]

Ahh, thank you. I can do that. Time to move on so and find the next hurdle!