SQL> declare
  2       e_user_err    exception;
  3       v_deptno  dept.deptno%type := &no;
  4  begin
  5       update dept set loc=‘HongKong‘ where deptno=v_deptno;
  6  
  7       if sql%notfound then
  8           raise e_user_err;
  9       end if;
 10       commit;
 11  exception
 12        when  e_user_err then
 13         dbms_output.put_line(‘This department ‘||v_deptno|| ‘ is not in dept table ,please input correct number !‘);
 14  end;

-------违背了参考性约束

declare
    e_emp_remain    exception;
    pragma exception_init( e_emp_remain ,-2292);
  
  v_deptno dept.deptno%type :=&no;
  
  begin
     delete from dept where deptno=v_deptno;
     commit;
  exception
     when e_emp_remain then
    dbms_output.put_line (‘Don‘‘t remove this ‘||v_deptno||‘  department !‘||‘ ,  This record is in emp !‘);
     when others then
    dbms_output.put_line (‘Others error !‘);     
 end;

SQL> declare
  2      e_emp_remain    exception;
  3      pragma exception_init( e_emp_remain ,-2291);
  4  
  5      v_empno emp.empno%type :=&n;
  6      v_deptno emp.deptno%type :=&nn;
  7  
  8    begin
  9       update emp set deptno=v_deptno where empno=v_empno;
 10       commit;
 11    exception
 12       when e_emp_remain then
 13      dbms_output.put_line (‘Department is not exists !‘);
 14       when others then
 15      dbms_output.put_line (‘Others error !‘);
 16   end;

SQL> declare
   2     v_code errors.code%type;
   3     v_msg  errors.msg%type;
   4     v_sal  emp.sal%type;
   5   
   6      begin
   7        
   8     select sal into v_sal from emp where deptno=&no;
   9     
  10  exception
  11      when no_data_found then
  12      dbms_output.put_line(‘No this department ID‘);
  13      when others then
  14       dbms_output.put_line(‘Others error ‘);
  15       v_code := sqlcode;          
  16       v_msg := sqlerrm;   
  17     dbms_output.put_line(v_msg);
  18               
  19     insert into errors values(v_code,v_msg);
  20     commit;    
  21  end;

SQL> declare
  2      e_emp_err    exception;
  3      pragma exception_init( e_emp_err ,-1422);
  4  
  5     v_sal emp.sal%type;
  6  
  7    begin
  8       select sal into v_sal from emp where deptno=&no;
  9       commit;
 10    exception
 11       when e_emp_err then
 12      dbms_output.put_line (‘ Return rows more than one row !‘);
 13       when others then
 14      dbms_output.put_line (‘Others error !‘);
 15   end;