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Can any one help me solve this small problem I have.

Senario.

I have set up a test table with one record in which i increment the value of one field.

I edit the database , increment the field and update it. I am using cached updates and transactions.

It all works fine until i have two user doing the same thing.

I have implemented locking.

I get an error 'Update failed 0 Records found' when the second user tries to update the table.


Here is my sample code - 'tb' is my table - 'mysql' is my mysqlconnection

procedure TForm1.Button1Click(Sender: TObject);
var
lck:integer;
begin

lck:=0;
tb.active:=true;
tb.refresh;
mysql.StartTransaction;

try
tb.LockTable (ltwrite)
except
showmessage ('locked');
mysql.rollback;
lck:=1;

end;
if lck=0 then begin
tb.refresh;
tb.edit;
tb.Fields[0].AsInteger :=tb.Fields[0].AsInteger +1;
tb.post;

tb.ApplyUpdates;
tb.CommitUpdates ;
mysql.Commit;
label1.caption:=tb.Fields[0].asstring;
label1.Refresh;
tb.UnLockTable;

end;
lck:=0

end;

Thanks

Do you have set the primary for this table? This error will occur if your table does not have unique key...

If you need to be sure that the only user updates a table at the single moment you should add unique autoincrement field to your table.

PS: Most probably, CachedUpdates not needed in this case.