Question

鉴于下表：

ID | Name         | Time       | Parent
 1 | Orange       | 1493596800 | 0
 2 | Apple        | 1483228800 | 0
 3 | Red Apple    | 1493596800 | 2
 4 | Yellow Apple | 1493769600 | 2

我希望按子行的下降时间对表进行排序，并过滤行，使Parent必须为零。

例如：

SELECT * 
  FROM MyTable as mt1 
 WHERE Parent = 0 
 Order 
    BY 
     ( SELECT mt2.Time 
         FROM MyTable mt2 
        WHERE mt2.Parent = mt1.ID
     Order BY mt2.Time DESC
        Limit 1
     ) DESC

**输出必须为：**

 2 | Apple        | 1483228800 | 0
 1 | Orange       | 1493596800 | 0

Answer 1

SELECT p.ID, p.Name, MAX(c.Time) AS NewestChildTime, p.Parent
FROM MyTable p
LEFT OUTER JOIN MyTable c
ON c.Parent = p.ID
WHERE p.Parent = 0
GROUP BY p.ID, p.Name, p.Parent
ORDER BY NewestChildTime DESC

Answer 2

select a.* from MyTable a
left join 
(
select a.name,max(b.time) time,b.parent from MyTable a
join MyTable b on b.parent=a.id
where b.parent>0 group by a.name,b.parent 
) b on b.parent=a.id
where a.parent=0
order by b.time desc

SQL基于子行值对表中的父行进行排序

2 个答案: