为什么我的MySQL查询很慢？

Question

Background: 
entities tables currently has 14,111 records 
articles table currently has 5211 records 

我想找到是有效的（完成）的所有文章，并有实体“谷歌”

# Finding articles that have the entity google takes: 
# 4 ms 
SELECT `Article`.`id` FROM `articles_entities` AS `ArticlesEntity` 
LEFT JOIN `entities` AS `Entity` ON (`ArticlesEntity`.`entity_id` = `Entity`.`id`) 
WHERE `Entity`.`strict` = 'google' 

# Finding articles that have the entity google and is active takes: 
# 1800 ms 
SELECT `Article`.`id` FROM `articles_entities` AS `ArticlesEntity` 
LEFT JOIN `entities` AS `Entity` ON (`ArticlesEntity`.`entity_id` = `Entity`.`id`) 
LEFT JOIN `articles` AS `Article` ON (`ArticlesEntity`.`article_id` = `Article`.`id`) 
WHERE `Entity`.`strict` = 'google' AND `Article`.`state` = 'completed' 

什么可能是与查询需要如此长的问题？

我想补充一点，数据透视表中的两个字段都是索引的。

在此先感谢您的帮助

UPDATE

id select_type table type possible_keys key key_len ref rows Extra 
1 SIMPLE Entity ref PRIMARY,strict strict 767 const 1 Using where 
1 SIMPLE ArticlesEntity ref article_id,entity_id,article_id_2 entity_id 108 b2b.Entity.id 4 
1 SIMPLE Article eq_ref PRIMARY,state PRIMARY 108 b2b.ArticlesEntity.article_id 1 Using where 

Answer 1

Entity.strict或Article.state不被索引。 在您的SELECT语句之前使用EXPLAIN并检查哪些表正在被完全扫描。这将暗示需要编制索引的内容。

Answer 2

你真的需要左连接吗？！恕我直言，你的查询应该得到一个提升没有它;）