Question

以下使用双嵌套子查询的mysql查询太慢

SELECT t.name
FROM creatives AS c
INNER JOIN term_relationships AS tr ON tr.creative_id=c.creative_id
INNER JOIN terms AS t ON t.term_id=tr.term_id
WHERE c.creative_id IN
   (SELECT creative_id
    FROM term_relationships
    WHERE term_id IN
       (SELECT offer_term_id
        FROM offer_urls))
AND t.taxonomy LIKE 'ad_network';

内部查询

SELECT creative_id
    FROM term_relationships
    WHERE term_id IN
       (SELECT offer_term_id
        FROM offer_urls)

非常快（0.04秒）

但完整查询并未提供结果。等了大约5分钟后我放弃了。

有什么办法优化这个？

Answer 1

尝试：

SELECT t.name
FROM creatives AS c
JOIN term_relationships AS tr ON tr.creative_id=c.creative_id
JOIN terms AS t ON t.term_id=tr.term_id
JOIN term_relationships tr2 ON tr2.creative_id = c.creative_id
JOIN offer_urls ou ON ou.offer_term_id = tr2.term_id
WHERE t.taxonomy LIKE 'ad_network';

这个只用JOIN编写的版本会更快。

Answer 2

尝试使用exists：

重写此内容

SELECT t.name
FROM terms t JOIN
     term_relationships tr
     ON t.term_id = tr.term_id JOIN
     creatives c
     ON tr.creative_id = c.creative_id
WHERE EXISTS (SELECT 1
              FROM term_relationships tr2 JOIN
                   offer_urls ou
                   ON tr.term_id = ou.offer_term_id
              WHERE c.creative_id = tr2.creative_id
             ) AND
     t.taxonomy LIKE 'ad_network';

然后为此您需要以下索引：

terms（taxonomy，term_id）
offer_urls（offer_term_id）
term_relationships（creative_id，term_id）;
素材（CREATIVE_ID）

您可能已经使用主键定义定义了其中一些。

嵌套子查询太慢

2 个答案: