Question

我有一个包含两个表的数据库：

subscriber_mm
uid_local   | uid_foreign   | uid_partner   
7           |2              |0      
7           |4              |0      
2           |1              |0  
2           |2              |0  
5           |1              |0      
5           |3              |0

partner_mm
uid_local   | uid_foreign   | uid_partner 
7           |1              |1

我的目标是根据两个表计算uid_local的总行数例如：

count both tables by uid_local = 7

结果：3

示例：

count both tables by uid_local = 2

结果：2

这是我没有WHERE语句的解决方案（不是最好的）

SELECT sum(
ROWS ) AS total_rows
FROM (
SELECT count( * ) AS ROWS
FROM partner_mm
UNION ALL
SELECT count( * ) AS ROWS
FROM subscriber_mm
) AS u

我该如何实现WHERE语句？

Answer 1

此处为您的查询传递值而不是2：

select sum(total_count ) as total_count  from 
(select count(*) as total_count from subscriber_mm s where s.uid_local=2
union all 
select count(*) as total_count from partner_mm m where m.uid_local=2) as a

或

 select a.uid_local,sum(total_count ) as total_count  from 
    (select s.uid_local as uid_local, count(*) as total_count from subscriber_mm s group by s.uid_local
    union all 
    select m.uid_local as uid_local, count(*) as total_count from partner_mm m group by m.uid_local) as a  
group by a.uid_local

Answer 2

无需执行SUM，因为您只需要计算特定uid_local的两个表返回的总行数。可以使用UNION ALL运算符获取总行数，这些运算符从两个表 WITHOUT 返回的结果集中删除重复记录

Select count(*) as Result From

(

Select * from subscriber_mm
where uid_local=7
union all
Select * from subscriber_mm
where uid_local=7

)as tmp

Answer 3

请尝试

    select  uid_local,uid_foreign,uid_partner from subscriber_mm
union
select uid_local,uid_foreign,uid_partner from partner_mm

您可以使用Union For sum两个表行

两个表的总和行

3 个答案: