Record your life!
Dashboard
My Blogs
← Back to List
Create Blog
Title
Type
Diary
Blog
Category
Database
Content
Edit
Preview
- Pivot 和 Unpviot的概念，把列塞入行，和把行塞入列 - Unnest的概念，把tuple转换成行 - 造数据并且自测 ``` with ( Select 10 as count, "a" as name union all Select 20, "b" union all select 30, "c" ) as test select * from test ``` - cross join就是纯笛卡尔积，cross join + where a.id = b.id <=> inner join - group by rollup 是BI中经常用的概念， group by rollup(a,b) 等同于把 group by a,b, group by a 和group by ()三个结合在一起，同时返回三个维度的数据
Update