0

我正在执行这个查询，结果很好，但问题是它花费了太长时间，有人可以告诉我如何提高效率（SQL 显示这个查询需要 2.8 秒，但实际上它需要超过 10 秒）起初我在 3 个表上使用连接，但该查询比这个查询花费更多时间。提前致谢。

SELECT 
    ee_expert.expert_id , 
    AVG( ee_expert_rating.rating_stars ) AS total_rating, 
    ee_expert.expert_id, 
    COUNT( DISTINCT ee_expert_rating.rating_id ) AS rating_count 
FROM 
    ee_expert_rating 
        RIGHT JOIN ee_expert 
            ON ee_expert.expert_id = ee_expert_rating.expert_id 
WHERE 
    expert_verified_email =2 
    AND expert_brief_description != '' 
    AND expert_account_status =1 
    AND ee_expert.expert_id IN 
        (
            SELECT 
                expert_id 
            FROM 
                ee_expert_categories 
            WHERE 
                ee_expert_categories.category_id =5 
            GROUP BY 
                expert_id 
        ) 
GROUP BY 
    ee_expert.expert_id 
ORDER BY 
    rating_count DESC
4

2 回答 2

1

这应该更快一点：（删除了内联组，并且在这种情况下使用存在可以提供帮助。）

SELECT
    ee_expert.expert_id ,
    AVG( ee_expert_rating.rating_stars ) AS total_rating,
    COUNT( DISTINCT ee_expert_rating.rating_id ) AS rating_count
FROM
    ee_expert_rating RIGHT JOIN
    ee_expert ON ee_expert.expert_id = ee_expert_rating.expert_id
WHERE
    expert_verified_email =2 AND          
    expert_brief_description != '' AND    
    expert_account_status =1 AND          
    exists(                               
        SELECT                            
            expert_id                     
        FROM                              
            ee_expert_categories
        WHERE
            ee_expert_categories.category_id =5 and
            ee_expert_categories.expert_id=ee_expert.expert_id
    )
GROUP BY
    ee_expert.expert_id
ORDER BY
    rating_count DESC

（尝试保留 IN 也/没有内部组。）

于 2013-10-01T11:22:02.913 回答
1

两件事减慢了整个事情的速度：

  1. 这需要10秒，因为通过网络传输数据，并以HTML（phpMyAdmin？）显示，它比实际语句慢。这只是一个猜测，但在 98% 的情况下都是正确的。

  2. 使用 subselect inIN()总是很慢（我认为是因为它为每个父数据集递归运行）。一个选项将使用EXISTS()

于 2013-10-01T11:23:06.240 回答