这是我的表数据….

id  days
-----------
1   10
    20
3   30
4   25
5   5

我想要结果

id  days    resultcolumn
1    10   less than 10
2    20   less than 20
3    30   less than 30
4    25   less than 30
5    5    less than 10

我用过查询

SELECT id,days,CASE days 
    WHEN days<=10 THEN 'less than 10'
    WHEN days<=20 THEN 'less than 20'
    WHEN days<=30 THEN 'less than 30'
  END AS 'days2'
FROM calender

但我得到了结果数据

id  days    resultcolumn
1   10    {null}
2    20   {null}
3    30   {null}
4    25   {null}
5    5    {null}

如何在MysqL中使用case语句获取原始结果？