Question

我有以下查询，其中将两个表的计数相除，并显示其他列值。

两个表都通过月/年连接。

  select 
        (a.count_one / b.count_two) as final_count, a.orders,
        a.Months, b.Sum
    from 
        (
            select count(*) as count_one, DATE_FORMAT(`date`, "%M %Y") AS `Months`, orders 
            from first_table
            GROUP BY Months)
        ) a
    INNER JOIN
        (
            select count(*) as count_two, DATE_FORMAT(`date`, "%M %Y") AS `Months`, sum(a) AS Sum
            from second_table
            GROUP BY Months)
        ) b
    ON a.Months = b.Months

输出：

**Month and Year**    **Final_Count**
January 2016              126
February 2016             123
March 2016                 45
....                      ....
...                       ....
...                       ....

What is required?

存在第三个表，其键在first_Table和second_table中。我需要根据第三个表放置一个WHERE子句，即WHERE thirdtable.name ='Any name'

因此，无论出现与thirdtable.name相关的ID的什么地方，这些结果都应显示，但我无法实现。

我尝试了什么？

我尝试了第三次INNER加入AS：

INNER JOIN third_table ON a.shid= third_table.id WHERE thirdtable.name='Any name'

但是，在这种情况下，不会显示任何结果。

有什么建议吗？

Answer 1

子查询不会选择id列，因此没有a.shid要比较。而且，由于子查询是按月分组的，因此您无法在其中选择id列。

您需要与子查询中的第三个表联接。

select 
    (a.count_one / b.count_two) as final_count, a.orders,
    a.Months, b.Sum
from 
    (
        select count(*) as count_one, DATE_FORMAT(`date`, "%M %Y") AS `Months`, orders 
        from first_table
        JOIN third_table ON first_table.shid = third_table.id
        WHERE third_table.name = 'Any name'
        GROUP BY Months)
    ) a
INNER JOIN
    (
        select count(*) as count_two, DATE_FORMAT(`date`, "%M %Y") AS `Months`, sum(a) AS Sum
        from second_table
        JOIN third_table ON second_table.shid = third_table.id
        WHERE third_table.name = 'Any name'
        GROUP BY Months)
    ) b
ON a.Months = b.Months

在MySQL的第三个表中添加WHERE子句，其ID在前两个内部联接表中存在

1 个答案: