SET SERVEROUTPUT ON（无知真可怕）

You will get the following output (assuming the grade of employee no 1 is ‘A’):
Employee Grade is A
PL/SQL procedure successfully completed.

NND，搞了好长时间，只出现“PL/SQL过程已成功完成”

就是不输出结果，我的去！

无知真可怕，希望早日脱离无知！