hive 可以通过with查询来提高查询性能，因为先通过with语法将数据查询到内存，然后后面其它查询可以直接使用，这种方法与创建临时表类似但是不需要创建临时表实体表，内存中的子查询结果在会话结束后会自动删除。
with q1 as ( select key from src where key = '5') select * from q1; -- from style with q1 as (select * from src where key= '5') from q1 select *; -- chaining CTEs with q1 as ( select key from q2 where key = '5'), q2 as ( select key from src where key = '5') select * from (select key from q1) a; -- union example with q1 as (select * from src where key= '5'), q2 as (select * from src s2 where key = '4') select * from q1 union all select * from q2;
转载于:https://www.cnblogs.com/shujuxiong/p/9910052.html
