Nested Blocks in PL/SQL

PL/SQL 中提供 Nested Blocks 的功能, 其目的為:
* Use to handle exception locally (Codes from Tony Andrews):

begin
   for emp_rec in (select * from emp) loop
      begin
         my_proc (emp_rec);
      exception
         when some_exception then
            log_error('Failed to process employee '||emp_rec.empno);
      end;
   end loop;
end;

* Declare local variables that have limited scopes (Codes from Tony Andrews);

declare
    l_var1 integer;
    -- lots of variables
begin
   -- lots of lines of code
   ...
   for emp_rec in (select * from emp) loop
      declare
         l_localvar integer := 0;
      begin
         -- Use l_localvar
         ...
      end
   end loop;

end;

Reference:
When should I nest PL/SQL BEGIN…END blocks? (http://stackoverflow.com/questions/2334659/when-should-i-nest-pl-sql-begin-end-blocks)