hive - 从 Hive 中的多个表中选择 count(*)

Question

我在 2 个不同的模式中有同名的表。我想要做的是在格式的 2 个表中进行计数比较

表名：Count1：Count2

如何通过 Hive 查询实现这一点？

Answer 1

使用 UNION ALL：

select 'db1.table_name' table_name, count(col1) count1, count(col2) count2 from db1.table_name
UNION ALL
select 'db2.table_name' table_name, count(col1) count1, count(col2) count2 from db2.table_name

Answer 2

您可以执行cross join计数查询。

select t1.count1,t2.count2
from (select count(*) as count1 from tbl1) t1
cross join (select count(*) as count2 from tbl2) t2

Answer 3

尝试完全外连接

select tt1.cn,tt2.cn from 
    (select count(1) as cn from db1.table) tt1 
full outer join 
    (select count(1) as cn from db2.table ) tt2
on tt1.cn=tt2.cn;