Mysql查询执行时间太长

SELECT pu.products_id, count(pu.products_id) as products_count, p.products_name,
pu.time_used FROM products_used pu, products_language_description p
WHERE pu.merchant_id='69'
AND p.products_id=pu.products_id GROUP BY products_id ORDER BY products_count
DESC LIMIT 0, 20

CREATE TABLE `products_used` (
    `products_used_id` INT(15) NOT NULL AUTO_INCREMENT,
    `plans_key` VARCHAR(255) NOT NULL DEFAULT '0',
    `products_id` BIGINT(20) NOT NULL DEFAULT '0',
    `customers_id` INT(10) NOT NULL DEFAULT '0',
    `merchant_id` INT(10) NOT NULL DEFAULT '0',
    `time_used` DATETIME NOT NULL DEFAULT '0000-00-00 00:00:00',
    PRIMARY KEY (`products_used_id`),
    INDEX `plans_key` (`plans_key`)
)
COLLATE='latin1_swedish_ci'
ENGINE=MyISAM
AUTO_INCREMENT=24625441;
CREATE TABLE `products_language_description` (
    `products_id` INT(5) NOT NULL DEFAULT '0',
    `products_description` LONGTEXT NOT NULL,
    `products_name` TEXT NOT NULL COLLATE 'utf8_general_ci',
    `products_help_info` LONGBLOB NOT NULL,
    `products_language` VARCHAR(255) NOT NULL DEFAULT '',
    PRIMARY KEY (`products_id`, `products_language`)
)
COLLATE='latin1_swedish_ci'
ENGINE=MyISAM;

尝试添加索引到product_id &products_used表中的merchant_id字段

看看你的WHERE节。

,pu.merchant_id = ' 69 '和p.products_id =聚氨酯。products_id GROUP BY products_id

你正在比较两种不同的数据类型:

• products_id INT (5) NOT NULL默认"0",
• products_id bigint (20) not null default '0'，

还有，你用了不必要的单引号:

• pu.merchant_id = "69"

也许你需要在第一种情况下创建一些索引。外键也有帮助!

也许这对你有帮助!

对于这个查询:

SELECT pu.products_id, count(pu.products_id) as products_count,
       p.products_name, pu.time_used
FROM products_used pu join
     products_language_description p
     on p.products_id = pu.products_id
WHERE pu.merchant_id = '69'
GROUP BY pu.products_id
ORDER BY products_count DESC
LIMIT 0, 20

你想在products_used(merchant_id, products_id)上建立索引。在MySQL中，有时您可以使用关联子查询重写聚合查询以改进结果:

SELECT pu.products_id,
       (select count(*)
        from products_language_description p
        where p.products_id = pu.products_id
       ) as products_count,
       p.products_name, pu.time_used
FROM products_used pu
WHERE pu.merchant_id = '69'
ORDER BY products_count DESC
LIMIT 0, 20;

这将外部group by替换为相关查询中的一个聚合，应该只使用主键索引。

编辑:

等。你的问题是这两个定义:

CREATE TABLE `products_used` (
    . . . 
    `products_id` BIGINT(20) NOT NULL DEFAULT '0',
)
   . . .
CREATE TABLE `products_language_description` (
    `products_id` INT(5) NOT NULL DEFAULT '0',
     . . . 
)

连接条件使用不同的数据类型。修复表结构，使列具有相同的类型(使用alter table . . .)或通过重建它们

正如Gordon所提到的，我会将你的产品使用表的索引扩展到(merchant_id, product_id, time_used)，所以它是一个覆盖索引，而不必去原始数据来获得你的count()。现在，对于给定的商家，在products_used表中有多个相同的"products_id"实例，这对我来说似乎很奇怪，但这是另一回事。

我会做产品ID的内部预查询，计数和时间具体到你想要的商人。否则，就像Gordon的查询示例一样，我首先预先查询每个产品，然后再为商家获取这些产品。

我建议预先查询商家特定使用的内部产品，然后一旦返回，获取产品名称。

SELECT 
      JustByMerchant.products_id, 
      JustByMerchant.products_count, 
      p.products_name,
      JustByMerchant.time_used 
   FROM
      ( select 
              pu.products_id, 
              count(*) as products_count, 
              pu.time_used 
           from
              products_used pu
           where
              pu.merchant_id = 69
           group by 
              pu.products_id
           order by
              COUNT(*) DESC
           limit 
              0, 20 ) JustByMerchant
        JOIN products_language_description p
           ON JustByMerchant.products_id = p.products_id