Hive中join时，如果关联的key值null则会过滤掉该行，看如下演示：

建表并插入数据

create table tmp.bbb as select 1/0 as id, 'a' as a;

create table tmp.aaa as select 1/0 as a, 'a' as a;

表tmp.aaa

表tmp.bbb

JOIN关联

select * from tmp.aaa a join tmp.bbb b on a.id = b.id;

结果