Question

以下查询会在上传到我的外部服务器时对页面加载产生负面影响：

SELECT 
   compositions.composer, compositions.composition, compositions.date, compositions.performedBy
FROM 
   compositions
   INNER JOIN
   (SELECT composer 
    FROM compositions  
    WHERE 
      composer IN (
         SELECT composer FROM compositions 
         GROUP BY composer 
         HAVING COUNT(1) < 15
      )
    ORDER BY RAND()
    LIMIT 1) AS RandComposer
ON 
   compositions.composer = RandComposer.composer
ORDER BY compositions.composition

总页面加载时间超过4秒，其中大部分是由于包含查询的PHP页面的等待时间（see Pingdom screenshot）。

表格中的所有相关字段＆＃39;组合＆＃39;被编入索引（see phpMyAdmin screenshot）。

我也可以在phpMyAdmin中提供EXPLAIN的输出，但我没有足够的声誉来发布第三个链接。

如果有人可以查看查询并告知如何改进查询以减少页面加载时间，我将非常感激。

Answer 1

重新构建查询解决了问题。以下代码会立即加载。

SELECT 
compositions.composer, compositions.composition, 
compositions.date, compositions.performedBy
FROM 
    compositions 
INNER JOIN
    (
        SELECT composer FROM compositions 
        GROUP BY composer 
        HAVING COUNT(*) < 15
        ORDER BY RAND()
        LIMIT 1
    ) AS RandComposer
ON 
    compositions.composer = RandComposer.composer
ORDER BY 
    compositions.composition;

MySQL查询减慢了外部服务器上的页面加载速度

1 个答案: