MySql - 具有特定字段计数的列表

Question

在列出特定字段时如何计算？ 对于我的示例（在图像上），COUNT_ROWS 的预期结果应该是：

/App/RaspLot - 2;
/App/RaspLot - 2;
/Home/ePortal_Options - 2;
/Home/ePortal_Options - 2;
/Home/ePortal_Logout - 1;

下图的当前结果：

我在努力：

SELECT T.`MAIN_PATH`, A.`SUB_PATH`, T.`COUNT_ROWS`
FROM `SIDENAV` A 
INNER JOIN (
    SELECT `MAIN_PATH`,  COUNT(DISTINCT `MAIN_PATH`) AS `COUNT_ROWS` 
    FROM `SIDENAV` 
    GROUP BY `MAIN_PATH`
) T ON A.`MAIN_PATH` = T.`MAIN_PATH` 
ORDER BY `ORDER_1`, `MAIN_NAME`, `ORDER_2` ASC 

Answer 1

看起来你真的只是想要聚合：

select main_path, count(*) as count_rows
from sidenav
group by main_path
order by count_rows desc, main_path

如果你想要每一行的计数，你可以使用窗口函数：

select s.*, count(*) over(partition by main_path) as count_rows
from sidenav s

这需要 MySQL 8.0。在早期版本中，您可以使用子查询执行窗口计数：

select s.*,
    (select count(*) from sidenav s1 where s1.main_path = s.main_path) as count_rows
from sidenav s