我正在创建一个论坛,需要一点反馈。我一直在编程很长一段时间,但我对MySQL很熟悉,并且想知道我是否正确地做了这件事。优化我的MySQL查询
这是我用来输出所选论坛的thr主题索引的查询。我试图在单个查询中收集所有信息,而不是仅收集主题信息,然后在每个循环的每个循环中收集一次帖子和成员信息,总计达到35个单独查询(每个主题一个 )。明白了吗?
基本上,它的工作原理。它有点慢(大约1秒),即使只有300-400个话题。
我用分析,并聚集了最耗时的操作是: 复制到tmp下表:0.538037 发送数据:0.206218 复制到组表:0.137549
编辑: 查询会每次有人进入页面时运行一次(通过网站活动判断,每小时约200-300次)。我打算每次检索大约4000-5000行。
我的问题是:这是最好的方法吗?有什么我可以做,以优化此查询?或者我会更好地在循环内部执行很多较小的查询吗?
$user_id: id of the user
$forum_id: id of the selected forum
SELECT
# Topic records
`topics`.*,
# First Post
GROUP_CONCAT(`posts`.`id`) AS `post_id`, # All post ids
`posts`.`post` AS `post_first_msg`,
`posts`.`date` AS `post_first_date`,
`posts`.`member` AS `post_first_member`,
# First member
`members`.`id` AS `member_id`,
`members`.`username` AS member_username,
# Returns last 3 members' id
SUBSTRING_INDEX(
GROUP_CONCAT(`members`.`id` ORDER BY `posts`.`date` DESC SEPARATOR '\\\\'), '\\\\', 3
) AS member_last_id,
# Returns last 3 members' username
SUBSTRING_INDEX(
GROUP_CONCAT(`members`.`username` ORDER BY `posts`.`date` DESC SEPARATOR '\\\\'), '\\\\', 3
) AS member_last_username,
# Get last viewed topic id
`member_topic_lastview`.`lastview` AS `lastview`
FROM
`topics`
# Returns the `posts` table in ASC order
JOIN (
SELECT *
FROM `posts`
ORDER BY `posts`.`date` ASC
) AS `posts` ON `posts`.`topic` = `topics`.`id`
# Member table, only the columns needed
JOIN (
SELECT
`members`.`id`,
`members`.`username`
FROM `members`
) AS `members` ON `members`.`id` = `posts`.`member`
# Forum table, containing the forum info
LEFT JOIN `forum` ON `forum`.`id` = `topics`.`forum`
# Table containing the latest viewed post id of each topic
LEFT JOIN (
SELECT *
FROM `member_topic_lastview`
WHERE `member_topic_lastview`.`member` = '$user_id'
) AS `member_topic_lastview` ON `member_topic_lastview`.`topic` = `topics`.`id`
WHERE
`forum` > $forum_id
GROUP BY
`topics`.`id`
ORDER BY
`topics`.`sticky` DESC,
MAX(`posts`.`date`) DESC
LIMIT 35
非常感谢!
如何经常干这种查询需要运行?您打算查询多少数据? – tadman 2013-02-11 22:25:02
你在各种表格上有什么样的索引? – Melanie 2013-02-11 22:29:00
每次有人进入该页面时,该查询将会运行一次(通过网站活动判断,每小时约200-300次)。我打算每次检索大约4000-5000行。如果你喜欢,我可以找出尺寸。 – Tom 2013-02-11 22:30:19