SQL：查询复杂的子查询

Question

我在游戏的数据库下表：在globalRank表

rankedUp (image_id, user_id, created_at) 
globalRank (image_id, rank) 
matchups (user_id, image_id1, image_id2) 

所有image_ids被分配一个等级是从0浮子1

假设我有登录用户的“USER_ID”值目前，我正在寻找一个查询，将返回一对图像的IDS（imageid1，imageid2）使得：

1. imageid1具有更低的等级比imageid2，但也是未来最高的ra NK小于imageid2
2. 对决表不具有（用户ID，imageid1，imageid2）或（用户ID，imageid2，imageid1）
3. rankedup表不具有（用户ID，imageid1），或者如果是这样，createdat柱比X小时之前

我到目前为止的要求1，这是：

SELECT lowerImages.image_id AS lower_image, higherImages.image_id AS higher_image 
FROM global_rank AS lowerImages, global_rank AS higherImages 
WHERE lowerImages.rank < higherImages.rank 
AND lowerImages.image_id = ( 
    SELECT image_id 
    FROM (
     SELECT image_id 
     FROM global_rank 
     WHERE rank < higherImages.rank 
     ORDER BY rank DESC 
     LIMIT 1 , 1 
     ) AS tmp 
    ) 

，但它不工作，因为我不能在子查询中引用higherImages.rank。

有谁知道我怎么能满足所有这些要求在一个查询？

感谢您的帮助

编辑：

我现在有这个疑问，但我不知道的效率，我需要测试它的正确性：

SELECT lowerImages.image_id AS lower_image, 
     max(higherImages.image_id) AS higher_image 
FROM global_rank AS lowerImages, global_rank AS higherImages 
WHERE lowerImages.rank < higherImages.rank 

AND 1 NOT IN (select 1 from ranked_up where 
    lowerImages.image_id = ranked_up.image_id 
    AND ranked_up.user_id = $user_id 
    AND ranked_up.created_at > DATE_SUB(NOW(), INTERVAL 1 DAY)) 

AND 1 NOT IN (
    SELECT 1 from matchups where user_id = $userId 
      AND lower_image_id = lowerImages.image_id 
      AND higher_image_id = higherImages.image_id 
      UNION 
      SELECT 1 from matchups where user_id = $user_id 
      AND lower_image_id = higherImages.image_id 
      AND higher_image_id = lowerImages.image_id 
) 
GROUP BY 1 

的“不在“我使用的声明都是索引，所以他们应该快速运行。效率问题我已经是该组并选择global_rank表

---

的这个问题的Pretty Complex SQL Query修订，不应再回答。

Answer 1

select 
(
select image_id, rank from 
rankedup inner join globalRank 
on rankedup.image_id = globalRank .image_id 
where user_id = XXX 
limit 1, 1 
) as highest, 
(
select image_id, rank from 
rankedup inner join globalRank 
on rankedup.image_id = globalRank .image_id 
where user_id = XXX 
limit 2, 1 
) as secondhighest 

我通常使用SQL Server中，但是这个我觉得是翻译为MySQL :)

Answer 2

这应该做的伎俩：

SELECT lowerImages.*, higherImages.* 
FROM globalrank AS lowerImages, globalrank AS higherImages 
WHERE lowerImages.rank < higherImages.rank 
AND lowerImages.image_id = ( 
    SELECT image_id 
    FROM (
     SELECT image_id 
     FROM globalrank 
     WHERE rank < higherImages.rank 
     ORDER BY rank DESC 
     LIMIT 1,1 
     ) AS tmp 
    ) 
AND NOT EXISTS (
    SELECT * FROM matchups 
    WHERE user_id = $user_id 
    AND ((image_id1 = lowerImages.image_id AND image_id2 = higherImages.image_id) 
     OR (image_id2 = lowerImages.image_id AND image_id1 = higherImages.image_id)) 
) 
AND higherImages.image_id NOT IN (
    SELECT image_id FROM rankedup 
    WHERE created_at < DATE_ADD(NOW(), INTERVAL 1 DAY) 
    AND USER_ID <> $user_id 
) 
ORDER BY higherImages.rank 

我假设对决的PKS和排名包括这些表中的所有列。这将允许第二个2个子查询使用PK索引。您可能需要globalrank.rank上的有序索引来加速第一个子查询。