1
我有一个用户生成内容的表格,其中包含状态的ENUM格式列。 (待定,已批准,已批准,汽车,或拒绝)为了保持连接的眼睛对状态的最新内容的数量,我使用以下查询:在使用SUM时提高MySQL查询性能
mysql> SELECT DATE(dt_submitted) AS date,
COUNT(*) AS count,
SUM(IF(status='Approved', 1, 0)) as approved,
SUM(IF(status='Approved-auto', 1, 0)) as approved_auto,
SUM(IF(status='Rejected', 1, 0)) as rejected,
SUM(IF(status='Pending', 1, 0)) as pending
FROM post
WHERE dt_submitted > DATE_SUB(CURDATE(), INTERVAL 30 DAY)
GROUP BY date;
+------------+-------+----------+---------------+----------+---------+
| date | count | approved | approved_auto | rejected | pending |
+------------+-------+----------+---------------+----------+---------+
| 2011-11-22 | 131 | 124 | 0 | 7 | 0 |
| 2011-11-23 | 116 | 114 | 0 | 2 | 0 |
...
| 2011-12-21 | 690 | 674 | 5 | 11 | 0 |
| 2011-12-22 | 80 | 75 | 0 | 4 | 38 |
+------------+-------+----------+---------------+----------+---------+
31 rows in set (0.60 sec)
这几乎是完美的,但我很挑剔,想看看我能不能做得更快。 (在这台服务器上0.6秒很慢,并且表变化太频繁,无需担心将静态日期传递给缓存结果。)
如果我解释查询,它没有使用任何索引(status
已索引)。 (难道这是因为它引用了总和创建临时表?)
explain SELECT DATE(dt_submitted) AS date, COUNT(*) AS count, SUM(IF(status='Approved', 1, 0)) as approved, SUM(IF(status='Approved-auto', 1, 0)) as approved_auto, SUM(IF(status='Rejected', 1, 0)) as rejected, SUM(IF(status='Pending', 1, 0)) as pending FROM post WHERE dt_submitted > DATE_SUB(CURDATE(), INTERVAL 30 DAY) GROUP BY date;
+----+-------------+-------+------+---------------+------+---------+------+--------+----------------------------------------------+
| id | select_type | table | type | possible_keys | key | key_len | ref | rows | Extra |
+----+-------------+-------+------+---------------+------+---------+------+--------+----------------------------------------------+
| 1 | SIMPLE | post | ALL | NULL | NULL | NULL | NULL | 529902 | Using where; Using temporary; Using filesort |
+----+-------------+-------+------+---------------+------+---------+------+--------+----------------------------------------------+
1 row in set (0.00 sec)
那么,有什么我可以做优化表或重写查询,使这个更快?或者这个查询是否受限于可用系统资源的速度?
编辑:dt_submitted
没有索引。
您可以发布您的索引创建语句? – 2011-12-22 17:34:07
圣牛我是个白痴。当我看到dt_submitted实际上没有被索引时,即将发布SHOW CREATE。创建索引将时间缩短到0.1秒。 (现在我应该删除这个问题,或者我该如何最好地处理该问题?) – 2011-12-22 17:48:48
为该问题创建一个答案 – Ben 2011-12-22 17:56:56