BorlandTalk.com Borland discussion newsgroups   Archives   FAQ   Search   Memberlist   Usergroups   Register   Profile   Log in to check your private messages   Log in  OnUpdateData datasetprovider          BorlandTalk.com Forum Index -> Delphi Databases (Multi-Tier) View previous topic :: View next topic   Author Message Alessandro Guest Posted: Mon Mar 28, 2005 12:02 pm    Post subject: OnUpdateData datasetprovider Hi. I use Delphi 7 / DataSnap / SocketdConnection / MS SQL 2000 / Corelabs dbExpress driver I try put all bussiness logic in my midle tier. I have a case, that i have verify a value field in a table before update. Depending on the value i update data or return message erro to user. I do this in onUpdateData evento because all execute in this event is sent to database in one transaction. the code is: ------ SQLDataSet1.CommandText := 'select STATUS from Req where Req.Number = '+DataSet.FieldByName('Number').AsString; SQLDataSet1.Open; if SQLDataSet1.FieldByName('STATUS').AsString = 'R' then (***) raise Exceptiopn.create('message erro') ---- end event MY QUESTION IS: AS I GUARANTEE THAT BETWEEN CHECK THE VALUE AND THE COMAND IS EXECUTE IN DATABASE OTHER USER DONT CHANGE THIS FIELD? Thanks Alessandro Back to top Wayne Niddery [TeamB] Guest Posted: Mon Mar 28, 2005 4:59 pm    Post subject: Re: OnUpdateData datasetprovider Alessandro wrote: Quote: the code is: SQLDataSet1.CommandText := 'select STATUS from Req where Req.Number = '+DataSet.FieldByName('Number').AsString; SQLDataSet1.Open; if SQLDataSet1.FieldByName('STATUS').AsString = 'R' then (***) raise Exceptiopn.create('message erro') MY QUESTION IS: AS I GUARANTEE THAT BETWEEN CHECK THE VALUE AND THE COMAND IS EXECUTE IN DATABASE OTHER USER DONT CHANGE THIS FIELD? Do you mean in the case where Status is not 'R' and you proceed with the update? If so, then no there is no guarantee - another user could indeed update that record between your Select and Update statements - unless you place a lock on that record as part of the Select statement. If the status is the only value that needs to be checked to allow the update then you could change the logic to simply go ahead with the update and include that check in the Where clause: Update Req set <field assignments> where Req.Number = <value> and Status <> 'R' After executing this update, check the RowsAffected property of the dataset, if not 1 then someone else has updated that record and your update failed. -- Wayne Niddery - Logic Fundamentals, Inc. (www.logicfundamentals.com) RADBooks: http://www.logicfundamentals.com/RADBooks.html "The purpose of morality is to teach you, not to suffer and die, but to enjoy yourself and live." - Ayn Rand Back to top Charles Adriano - Brazil Guest Posted: Mon Mar 28, 2005 11:23 pm    Post subject: Re: OnUpdateData datasetprovider hi alessandro i think, the best way, do you create a sotored procedure in then SQL server and execute your bussiness logic... (start transaction, update and commit) ... for the simple fact of everything to be done in the server... and stored procedure will be return a status value for you... (in case of error message) charles... PD1 : sorry for my english... PD2 : i recommend Microsoft SQL Server 2000 DBA Survival Guide Mark Spenik and Orryn Sledge "Alessandro" <alessandrocamara (AT) hotmail (DOT) com> escribió en el mensaje news:4247f0dc (AT) newsgroups (DOT) borland.com... Quote: Hi. I use Delphi 7 / DataSnap / SocketdConnection / MS SQL 2000 / Corelabs dbExpress driver I try put all bussiness logic in my midle tier. I have a case, that i have verify a value field in a table before update. Depending on the value i update data or return message erro to user. I do this in onUpdateData evento because all execute in this event is sent to database in one transaction. the code is: ------ SQLDataSet1.CommandText := 'select STATUS from Req where Req.Number = '+DataSet.FieldByName('Number').AsString; SQLDataSet1.Open; if SQLDataSet1.FieldByName('STATUS').AsString = 'R' then (***) raise Exceptiopn.create('message erro') ---- end event MY QUESTION IS: AS I GUARANTEE THAT BETWEEN CHECK THE VALUE AND THE COMAND IS EXECUTE IN DATABASE OTHER USER DONT CHANGE THIS FIELD? 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