用SQL语句显示班级学号成绩并算出优良中差

select 班级,学号,(case when 成绩>90 then '优'
when 成绩>80 and 成绩<=90 then '良'
when 成绩>60 and 成绩<=80 then '中'
else '差' end) as 成绩
from table_name

swith(Fengsu){
case Fengsu>90
slevel="优";
case 80<=Fengsu<90
slevel="良";
case 60<=Fengsu<80
slevel="中";
case Fengsu<60
slevel="差";
}

swith(Fengsu){
case Fengsu>90
slevel="优";
case 80<=Fengsu<90
slevel="良";
case 60<=Fengsu<80
slevel="中";
case Fengsu<60
slevel="差"; select 班级,学号,(case when 成绩>90 then '优'
when 成绩>80 and 成绩<=90 then '良'
when 成绩>60 and 成绩<=80 then '中'
else '差' end) as 成绩
from table_name
}

select stuClassm,stuNo,成绩=case
when 列名 between<60 then '差'
when 列