use generators for the codes

[]s

>From: "Gustavo" <gusm@...>
>Reply-To: firebird-support@yahoogroups.com
>To: <firebird-support@yahoogroups.com>
>Subject: [firebird-support] Two users adding a record with the same code
>Date: Fri, 27 Jul 2007 10:08:22 -0300
>
>Hello:
>
>I will explain my problem with an example.
>
>Suppose I have a Table of ENTERPRISES with a field CODE (numeric), NAME,
>ADDRESS, etc. Then I have a table EMPLOYEES with a field ENTERPRCODE, NAME,
>AGE, ADDRESS, etc. Suppose there are already 100 entreprises in the table
>ENTERPRISES.
>
>1. User John begins to add a new enterprise. The application propose
>automatically the CODE 101 and John begins to add (in a grid) the
>employees. The field ENTERPRCODE of the employees he is adding will have
>the value 101.
>
>2. Almost at the same time (before John post his new enterprise), the user
>Peter begins to add a new enterprise. The application propose automatically
>the CODE 101 (the same as the one that is using John) and Peter begins to
>add (in a grid) the employees. The field ENTERPRCODE of the employees he is
>adding will have the value 101.
>
>3. John posts his enterprise.
>
>4. Peter posts his enterprise. At this moment, the application shows a
>message saying there is already an enterprise with CODE 101. Then Peter
>change the CODE to 102 and the application automatically changes the field
>ENTERPRCODE in the employees. Peter posts again his enterprise and
>everithing is OK.
>
>But...
>
>Supose that after item 3 (John posted his enterprise), for any reason Peter
>makes a refresh of the grid of employees. Then, as the refresh executes a
>SELECT * FROM EMPLOYEES WHERE ENTERPRCODE = "101", he will now see the
>employees that he (Peter) added and the ones that John added to his other
>enterprise that is already posted. This is wrong!
>
>This is a simplified explanation, but shows the problem.
>
>I think, it could be a solution if the SELECT done by the refresh could
>"see" only the records that are uncommited by the transaction in wich Peter
>is working. So it will not see the records commited by John. The question
>is: Is there a way to do this?
>
>Any other idea?
>
>I use FireBird 2.0, Delphi 5 and IBX.
>
>Thanks in advance
>
>Gustavo
>
>[Non-text portions of this message have been removed]
>

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