编写带参数的存储过程，将百分制成绩，转换成绩等级’A’,’B’,’C’,’D’,’E’

要求；

1. 存储过程要有输入和输出

create procedure chengji( in n int , out result varchar    )
begin 
  declare result varchar(20);
 set n=truncate(rand()*100,0);
 case
  when n>90 then
   set result='A';
  when n>80 then
   set result='B';
  when n>70 then
   set result='C';
  when n>60 then
   set result='D';
  else
   set result='E';
 end case;
 select n,result ;

end;
call chengji;create procedure RiQi( in n int , out result varchar (20)   )
begin

 case n
  when 0 then
   set result='星期日';
  when 1 then
   set result='星期一';
  when 2 then
   set result='星期二';
  when 3 then
   set result='星期三';
  when 4 then
   set result='星期四';
  when 5 then
   set result='星期五';
  else
   set result='星期六';
 end case;

end;
call RiQi(0,@result);
select @result;