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Oracle Interview Questions And Answers
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17. How many types of database triggers can be specified on a table ? What are they ? Insert Update Delete Before Row o.k. o.k. o.k. After Row o.k. o.k. o.k. Before Statement o.k. o.k. o.k. After Statement o.k. o.k. o.k. If FOR EACH ROW clause is specified, then the trigger for each Row affected by the statement. If WHEN clause is specified, the trigger fires according to the retruned boolean value. 18. Is it possible to use Transaction control Statements such a ROLLBACK or COMMIT in Database Trigger ? Why ? It is not possible. As triggers are defined for each table, if you use COMMIT of ROLLBACK in a trigger, it affects logical transaction processing. 19. What are two virtual tables available during database trigger execution ? The table columns are referred as OLD.column_name and NEW.column_name. For triggers related to INSERT only NEW.column_name values only available. For triggers related to UPDATE only OLD.column_name NEW.column_name values only available. For triggers related to DELETE only OLD.column_name values only available. 20. What happens if a procedure that updates a column of table X is called in a database trigger of the same table ? Mutation of table occurs. 21. Write the order of precedence for validation of a column in a table ? I. done using Database triggers. ii. done using Integarity Constraints. I & ii. Exception : 22. What is an Exception ? What are types of Exception ? Exception is the error handling part of PL/SQL block. The types are Predefined and user_defined. Some of Predefined execptions are. CURSOR_ALREADY_OPEN |