判断 no_data_found 异常 有大用 有大大用 有大大大用

declare 

max_salary_pf number;

begin

select max(salary) into max_salary_pf from my_emp where dept_id = 55;

  dbms_output.put_line('部门有员工');

  exception

    when no_data_found then

    dbms_output.put_line('此部门无员工');

end;

使用max(salary)  之后是有值的,不会抛出异常 

declare 

max_salary_pf number;

begin

select salary into max_salary_pf from my_emp where dept_id = 55;

  dbms_output.put_line('部门有员工');

  exception

    when no_data_found then

    dbms_output.put_line('此部门无员工');

end;

使用 salary  之后是没有值,会抛出异常