java - 在条件中选择带有 order by 的查询

Question

我想从此 SQL 查询创建一个条件查询：

SELECT * FROM `Product` p
ORDER BY (SELECT COUNT(*) FROM `Sale` WHERE `product_id` = p.id) DESC

我找不到使用子查询的方法...

Answer 1

尝试隐式连接：

select *
from (
    select 
         p.*, 
         (select count(*) from sale s where s.product_id = p.id) as cnt 
    from product p
)a 
order by cnt desc

Answer 2

Order By仅适用于select零件中存在的列。

所以基本上这样的事情会起作用：

SELECT Group, COUNT(*) as total
FROM table
GROUP BY Group
ORDER BY total DESC

因此，对于您的情况，您可以执行以下操作：

SELECT *, (SELECT COUNT(*) FROM `Sale` WHERE `product_id` = p.id) as total FROM `Product` p
ORDER BY total DESC

注意：这是完全未经测试的。