Question

我试图优化mysql查询，我用它来根据地址从数据库中获取客户。这个问题让我很生气，所以我很感激帮助：）

我有两个与此查询相关的表：customers_address和systems_address。我想只获得具有我可以为该系统显示的地址的客户。

示例：

我想从customers_address表中获取客户，其中address_id属于system_id 2.

使用in子句的最佳查询：

select distinct customer_id from customers_address use index(address_id_customer_id) where address_id in (select distinct address_id from systems_address where system_id = 2) and address_id !=-1\G;

事实是子查询只返回一行（值2），如果我用subquerys值运行整个查询，它真的很快：

select customer_id from customers_address use index(address_id_customer_id) where address_id !=-1 and address_id in (2)\G;

时间从10秒以上下降到0.00秒

我还尝试使用连接进行查询，但是当我将值替换为in子句时，与查询进行比较时，性能仍然很慢（超过7秒）。在带有连接的相同查询下面：

select distinct customer_id from customers_address use index(address_id_customer_id) inner join systems_address where systems_address.address_id = customers_address.address_id and system_id = 2 and customer_id != -1\G

我已将customers_address 816 000行和systems_address 400,000行放入。下面这些表的模式（简化表格，问题更容易找到）：

create table systems_address (
  `id` int(10) NOT NULL AUTO_INCREMENT PRIMARY KEY,
  `address_id` int(11) DEFAULT NULL,  
  `system_id` INTEGER(11)DEFAULT NULL,
   KEY `address_id` (address_id),
   KEY `system_id` (system_id))
  ENGINE=InnoDB AUTO_INCREMENT=4 DEFAULT CHARSET=latin1;

create table customers_address (
  `id` int(10) NOT NULL AUTO_INCREMENT PRIMARY KEY,
  `customer_id` int(11) DEFAULT NULL,  
  `address_id` INTEGER(11)DEFAULT NULL,
   KEY `customer_id` (customer_id),
   KEY `address_id` (address_id),
   KEY `address_id_customer_id` (address_id,customer_id),   
  FOREIGN KEY (`address_id`) REFERENCES `systems_address` (`address_id`) ON UPDATE CASCADE ON DELETE SET NULL)
  ENGINE=InnoDB AUTO_INCREMENT=4 DEFAULT CHARSET=latin1;

任何使查询更快的方法???

以下是我运行波希米亚查询时的解释结果（创建新索引和更新后）。

ID：1个
select_type：SIMPLE
表：系统地址
类型：参考
possible_keys：address_id，system_id，address_id_system_id，idx1，关键：IDX1 key_len：5 REF：常量行：1999 额外：使用where;使用临时

ID：2
SELECT_TYPE：SIMPLE
表：customers_address
类型：REF
possible_keys：customer_id，address_id，address_id_customer_id，idx2
关键：address_id_customer_id
key_len：5
裁判：database.systems_address.address_id
行：45375个
额外：使用where;使用索引

Answer 1

反转表的顺序并使用连接条件，其中包括额外条件：

select distinct customer_id
from systems_address
join customers_address on systems_address.address_id = customers_address.address_id
    and customer_id != -1
where system_id = 2

这应该非常好，使用索引并最小化访问的行数。

确保定义了以下索引：

create index idx1 on systems_address(system_id);
create index idx2 on customers_address(address_id);

为了确保，还要更新统计信息：

analyze systems_address, customers_address;

即使使用索引，Mysql查询仍然很慢

1 个答案: