qq_28388339的博客

转自：https://blog.youkuaiyun.com/ygdlx521/article/details/71156354 总结一下：两种表达方式是等效的 方法一： case when tb1.os = 'android' then 'android' when tb1.os = 'ios' then 'iPhone' else 'PC' end as os, 方法二： case tb1.os when 'android' then 'android' when 'ios' then 'iPhon