我正在尝试提高应用程序的性能。我可能需要创建在 cron 上运行的汇总表，这样应用程序的加载时间就不会太长（5-10 秒）。这是最好的主意吗？
给定下表：
mysql> describe school_data_sets_numeric_data;
+--------------+---------------+------+-----+---------+----------------+
| Field | Type | Null | Key | Default | Extra |
+--------------+---------------+------+-----+---------+----------------+
| id | int(11) | NO | PRI | NULL | auto_increment |
| data_set_nid | int(11) | NO | MUL | NULL | |
| school_nid | int(11) | NO | MUL | NULL | |
| year | int(11) | NO | MUL | NULL | |
| description | varchar(255) | NO | | NULL | |
| value | decimal(18,5) | NO | | NULL | |
+--------------+---------------+------+-----+---------+----------------+
6 rows in set (0.00 sec)
以及以下查询（为学校的每个 data_set_nid 运行一次）
此查询运行速度很快（0 秒）：
SELECT year, description, CONCAT(FORMAT((value/(SELECT SUM(value)
FROM `school_data_sets_numeric_data` as numeric_data_inner
WHERE year = numeric_data_outer.year and data_set_nid = numeric_data_outer.data_set_nid and school_nid = numeric_data_outer.school_nid)) * 100, 2), '%') as value
FROM `school_data_sets_numeric_data` as numeric_data_outer
WHERE data_set_nid = 38251 and school_nid = 32805 ORDER BY id DESC;
解释：
+----+--------------------+--------------------+------+---------------------------------------------+--------------+---------+-----------------------------------------------------------------------------------------------------------+------+-----------------------------+
| id | select_type | table | type | possible_keys | key | key_len | ref | rows | Extra |
+----+--------------------+--------------------+------+---------------------------------------------+--------------+---------+-----------------------------------------------------------------------------------------------------------+------+-----------------------------+
| 1 | PRIMARY | numeric_data_outer | ref | data_set_nid,data_set_nid_2,school_nid | data_set_nid | 8 | const,const | 17 | Using where; Using filesort |
| 2 | DEPENDENT SUBQUERY | numeric_data_inner | ref | year,data_set_nid,data_set_nid_2,school_nid | data_set_nid | 8 | rocdocs_main_drupal_7.numeric_data_outer.data_set_nid,rocdocs_main_drupal_7.numeric_data_outer.school_nid | 9 | Using where |
+----+--------------------+--------------------+------+---------------------------------------------+--------------+---------+-----------------------------------------------------------------------------------------------------------+------+-----------------------------+
此查询运行缓慢（1.43 秒）：
SELECT year, description, CONCAT(FORMAT((SUM(value)/(SELECT SUM(value)
FROM `school_data_sets_numeric_data` as numeric_data_inner
WHERE year = numeric_data_outer.year and data_set_nid = numeric_data_outer.data_set_nid)) * 100, 2), '%') as value
FROM `school_data_sets_numeric_data` as numeric_data_outer
WHERE data_set_nid = 38251 GROUP BY year,description ORDER BY id DESC;
解释：
+----+--------------------+--------------------+------+----------------------------------+----------------+---------+-------+-------+----------------------------------------------+
| id | select_type | table | type | possible_keys | key | key_len | ref | rows | Extra |
+----+--------------------+--------------------+------+----------------------------------+----------------+---------+-------+-------+----------------------------------------------+
| 1 | PRIMARY | numeric_data_outer | ref | data_set_nid,data_set_nid_2 | data_set_nid_2 | 4 | const | 90640 | Using where; Using temporary; Using filesort |
| 2 | DEPENDENT SUBQUERY | numeric_data_inner | ref | year,data_set_nid,data_set_nid_2 | year | 4 | func | 38871 | Using where |
+----+--------------------+--------------------+------+----------------------------------+----------------+---------+-------+-------+----------------------------------------------+