The check for existence of a match and the insertion of a new record are not protected by a lock, so there is a race condition.To do this reliably, you need to catch this exception and either re-run the merge or do a simple update instead.This course provides the essential SQL skills that allow developers to write queries against single and multiple tables, manipulate data in tables, and create database objects.
Can anyone please tell me where can I get information of DUAL and also about merge syntax?
(In Hibernate the solution is to open a new session/transaction just to execute this one Hi Adrian, I'm just thinking about a case where the UPDATE statement is only valid if the data has not changed since the attempted INSERT, and there are multiple processes performing the inserts and updates.
Unless all inserts and updates to the table are synchronized, sometimes the UPDATE may succeed and sometimes it may fail depending on how the processes interleave.
They learn about declaring variables, trapping exceptions and they also learn to declare and control cursors.
In class students learn to develop, execute and manage PL\SQL stored program units like procedures, functions, packages and database triggers.