hive sql使用记录

 

关于join 

推荐写法

SELECT 
        a.* 
        ,b.* 
FROM 
        (
                SELECT * 
                FROM a 
                WHERE {subquery_where_condition} 
        ) a 
{LEFT/RIGHT/FULL/LEFT SEMI/LEFT ANTI} JOIN 
        (
                SELECT * 
                FROM b
                WHERE {subquery_where_condition} 
        ) b 
ON {on_condition} 
WHERE {where_condition}
;

做表连接时，尽量将每个表的单表过滤条件单独写成子查询；而不要再join结束后再用where或者on去做单表过滤

要尽量的让参与join的两个表的数据量变小

https://cloud.tencent.com/developer/article/2242914

时间戳

https://blog.csdn.net/a805814077/article/details/115014708