Exception PL/SQL

PL/SQL error management features 
1- Defining exceptions
2- Raising exceptions 
3- Handing exceptions 

We will explain every topic individually

1-Defining exceptions

The EXCEPTION is a limited type of data. 
Has just two attributes: code and message. 
You can RAISE and handle an exception, but it cannot be passed as an argument in a program. 
syntax

pragma exception_init(error_name,-error_number);

example :-

declare

   bulk_erros exception

   pragma exception_init(bulk_erros,-20006);

begin

  ...

end;

2-Raising exceptions  
a-RAISE raises the specified exception by name. 
   RAISE; re-raises current exception. Callable only within the exception section. b-RAISE_APPLICATION_ERROR
  Communicates an application specific error back to a non-PL/SQL host environment.
  Error numbers restricted to the -20,999 - -20,000 range.
  Syntax :-

  RAISE_APPLICATION_ERROR (num binary_integer, msg varchar2, 

                                                                       keeperrorstack boolean default FALSE);

  Example :
  RAISE_APPLICATION_ERROR (-20070, ‘Employee must be more than 18 years old.’); 

3-Handing exceptions  

a-The EXCEPTION section consolidates all error handling logic in a block. 
b-We can use the following functions at exception section: 
   –SQLCODE --> get error number.
   –SQLERRM--> get error message.
   –DBMS_UTILITY.FORMAT_ERROR_STACK 
       Returns exception in more details.
   –DBMS_UTILITY.FORMAT_ERROR_BACKTRACE 
      Returns the full stack of errors with line number information.number that raised the error.
      This stack is available only if you the error is unhandled.
c-The DBMS_ERRLOG package 
   –Quick and easy logging of DML errors
d- We can use The AFTER SERVERERROR trigger to log any error have been raised at database.