Oracle的sql语句中case关键字的用法

create table tbl_score(
    id NUMBER(4), --id
    name varchar2(30), --名称
    score NUMBER(3), --分数
    otherscore NUMBER(3) --其他分数
);

select t.id as "_id",
       t.name as name,
       case
           when t.score >= 60 then
            ‘及格‘
           else
            ‘不及格‘
       end as ‘是否及格‘,
       t.score as ‘分数‘ 
  from tbl_score t;

select t.id as "_id",
       t.name as name,
       case
           when t.score is null then
            t.otherscore  --也可返回固定值
           else
            t.score
       end as ‘分数‘
  from tbl_score t;