An exception is an error which arises during the program execution. When an exception is raised, the normal program execution stops and the control transfers to the exception handling section if it exists; otherwise the program stops abruptly. There are two types of exceptions found in Oracle: predefined exceptions and user defined exception.
The predefined exceptions are raised automatically whenever there is a violation of Oracle coding rules, such as NO_DATA_FOUND being raised if a SELECT INTO statement returns no rows. For a complete list of predefined exceptions refer to Oracle Database PL/SQL Language Reference 11g Release 2.
Apart from the predefined exceptions, we can explicitly define exceptions based on business rules. These are known as user-defined exceptions. For example, an employee should be at least 18 years old; if he/she is less than 18 then the application should raise an error.
The stored procedure and function created in the previous sections do not...