>From: Terry Johnson [mailto:[EMAIL PROTECTED]]
>
>I've had problems with record locking - when a background process is trying
>to update a database that some user somewhere has left open during an edit.
Shurely locking issues would only occur during an uncommitted transaction?
>That's more of an underlying database issue, but the upshot was dbaware
>controls could not be used.
If it really was a showstopper you could still have used ClientDataSets,
running dbaware controls off them.
>Then there's always the problems of queries -
>the drama involved in updating a record returned in a read-only result set,
There are various non-dramatic ways to skin the "read-only result set" cat.
Eg., using RequestLive and CachedUpdates true:
procedure TForm1.qComplexQueryAfterPost(DataSet: TDataSet);
begin
qComplexQuery.ApplyUpdates;
end;
procedure TForm1.qComplexQueryAfterDelete(DataSet: TDataSet);
begin
qComplexQuery.ApplyUpdates;
end;
procedure TForm1.qComplexQueryUpdateRecord(DataSet: TDataSet;
UpdateKind: TUpdateKind; var UpdateAction: TUpdateAction);
procedure SetParams;
var i: integer;
begin
with qTemp do for i := 0 to Params.Count - 1 do begin
Params[i].ParamType := ptInput;
Params[i].DataType := DataSet.FieldByName(Params[i].Name).DataType;
Params[i].Value := DataSet.FieldByName(Params[i].Name).Value;
end;
end;
begin
inherited;
Database1.StartTransaction;
try
with qTemp, SQL do begin
Close;
Clear;
case UpdateKind of
ukInsert: begin
Add('insert into TABLE1');
Add(' (COL1, COL2, ...)');
Add('values');
Add(' (:PAR1, PAR2, ...)');
SetParams;
ExecSQL;
Clear;
Add('insert into TABLE2');
Add(' (COL1, COL2, ...)');
Add('values');
Add(' (:PAR1, PAR2, ...)');
SetParams;
ExecSQL;
end;
ukModify: begin
...
end;
ukDelete: ...
end;
end;
Database1.Commit;
UpdateAction := uaApplied;
except
Database1.Rollback;
raise;
end;
end;
That's just a trivial example to show how easy it can be. You can improve
on it a lot (especially to reduce its verboseness): generically pre-prepared
parameterised queries, UpdateSQLObjects, ClientDataSets, blah blah blah. :)
Still not nearly the effort required when you drop dbaware.
>and doing so in a way that is clean and intuitive to the user, and can be
>accomplished in a reasonable timeframe with large databases.
Hmmm... how does going non-dbaware deal with those issues any better?
Cheers,
Carl
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