MySQL---- 如何利用一条语句实现类似于if-else条件语句的判断

文章来源：https://www.cnblogs.com/areyouready/p/7588258.html

一 编写一条update语句实现商品涨价，具体规则如下：

1 99元以内，提价20%

2 100-999元之间，提价10%

3 1000-1999之间，提价5%

4 其他提价2%

update goods
set price=(
    case 
        when price between 0 and 99 then price *1.2
        when price between 100 and 999 then price *1.1
        when price between 1000 and 1999 then price * 1.05
        when priice > 1999 then price *1.02
    end
);
select * from goods;

二 编写一条select语句，实现如下效果

语句如下:

select username as 主攻,
(case
    when salary between 3000 and 5000 then “工资较低”,
    when salary between 5000 and 10000 then "工资一般",
    when salary between 10000 and 20000 then "工资较低",
    when salary between 20000 and 40000 then "工资还行",
    when salary between 40000 and 100000 then "膜拜"
end)
as 成绩
from students