Question

我有一个查询，该查询已记录在mysql慢日志文件中：

# Time: 2019-06-12T10:23:05.410474Z
# User@Host: coi[coi] @  [172.31.ip.ip]  Id:    91
# Query_time: 7.099090  Lock_time: 0.000065 Rows_sent: 0  Rows_examined: 
844952

use coi;
SET timestamp=1560334985;

SELECT  `trades`.* FROM `trades` 
    WHERE `trades`.`market_id` = 'omgeth' 
    AND (created_at > '2019-06-11 18:22:58.310183')  
    ORDER BY price 
    LIMIT 1;

在此，如何优化此查询？将索引添加到“ market_id和created_at”列？

该查询为什么检查844952条记录？如果我仅将索引添加到“ created_at”列怎么办？这会有所帮助吗？

这是我的表结构：

(this create table SQL comes from the "show create table" command) 

CREATE TABLE `trades` (
  `id` int(11) NOT NULL AUTO_INCREMENT,
  `price` decimal(32,16) DEFAULT NULL,
  `market_id` varchar(10) DEFAULT NULL,
  `created_at` datetime DEFAULT NULL,
  PRIMARY KEY (`id`),
  KEY `index_trades_on_created_at` (`created_at`) USING BTREE,
  KEY `index_trades_on_market_id` (`market_id`),
  KEY `index_trades_on_price` (`price`),

) ENGINE=InnoDB AUTO_INCREMENT=3509954 DEFAULT CHARSET=utf8

非常感谢！

Answer 1

对于此查询：

SELECT  t.*
FROM `trades` t
WHERE t.`market_id = 'omgeth' AND 
      t.created_at > '2019-06-11 18:22:58.310183'
ORDER BY t.price
LIMIT 1;

您要在trades(market_id, created_at)上建立索引。

如何优化此选择位置和“日期时间”的SQL？

1 个答案: