mysql – 优化大数据库中的SQL查询？

2023年5月7日 200次阅读

询问

SELECT *
FROM user_ip_tmp
WHERE too = 'http://example.com/'
AND contry != 'CN'
AND contry != 'TW'
ORDER BY id DESC
LIMIT 50

MySQL返回：

Showing rows 0 - 29 ( 50 total, Query took 11.9276 sec) [id: 3452538 - 3448824]

如果我删除
     ORDER BY id DESC

Showing rows 0 - 29 ( 50 total, Query took 0.0033 sec)

解释计划：

计数

SELECT count( * )
FROM user_ip_tmp

使用的数据库示例

CREATE TABLE IF NOT EXISTS `user_ip_tmp` (
  `id` int(9) NOT NULL AUTO_INCREMENT,
  `ip` varchar(20) NOT NULL,
  `dataip` bigint(20) NOT NULL,
  `ref` text NOT NULL,
  `click` int(20) NOT NULL,
  `code` varchar(17) NOT NULL,
  `too` text NOT NULL,
  `checkopen` varchar(17) NOT NULL,
  `contry` text NOT NULL,
  `vOperation` text NOT NULL,
  `vBrowser` text NOT NULL,
  `iconOperation` text NOT NULL,
  `iconBrowser` text NOT NULL,
  PRIMARY KEY (`id`),
  KEY `ip` (`dataip`),
  KEY `ip` (`checkopen`),
  KEY `ip` (`code`),
  KEY `ip` (`too`)
) ENGINE=MyISAM  DEFAULT CHARSET=utf8 AUTO_INCREMENT=5426268 ;

我想要正确的方法来进行查询并优化ORDER BY ID DESC的数据库

最佳答案 了解一些有关数据分布的信息会很有趣.您可以将以下查询的结果添加到您的帖子中吗？ (不需要图片,纯文本会做).

SELECT count(*) FROM user_ip_tmp WHERE too = 'http://example.com/' AND contry != 'CN' AND contry != 'TW'; 

SELECT count(*) FROM user_ip_tmp WHERE too = 'http://example.com/';

另外,您可以测试这种替代性能吗？编辑：子查询的别名

SELECT sub.* FROM
(SELECT *
FROM user_ip_tmp
WHERE too = 'http://example.com/'
AND contry != 'CN'
AND contry != 'TW'
) sub
ORDER BY sub.id DESC
LIMIT 50

编辑如果它是一个添加和试验索引的选项,那么你可以尝试其中一个(或两者都看看哪个更好)

CREATE INDEX index_name ON `user_ip_tmp` (`too`, `id`);
CREATE INDEX index_name ON `user_ip_tmp` (`too`, `contry`, `id`);
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