The Exceptions can be declared only in the declarative part of the PL/SQL subprogram, block, or package. By introducing its name, you can declare an exception followed by the keyword EXCEPTION. In the illustration below, you declare an exception named past_due:
The Exception and variable declarations are alike. But keep in mind that, an exception is an error condition, not a data item. Unlike variables, the exceptions cannot appear in the assignment statements or the SQL statements. Though, the same scope rules apply to the variables and exceptions.