多表查询？大家一般怎么用的？效率问题真的需要考虑吗?-PHP Tutorial-php.cn

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多表查询？大家一般怎么用的？效率问题真的需要考虑吗?

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Jun 06, 2016 pm 08:42 PM

mysqlphpdatabaseDatabase Design

【Order】表（OrderID，OrderDate，CustomerID）
【Customer】表（CustomerID，CustomerName，CustomerAddr，CustomerCity）

能给个案例代码吗？如何实现关联查询?
比如我要查询属于订单ID1的顾客信息。求tp代码

回复内容：

【Order】表（OrderID，OrderDate，CustomerID）
【Customer】表（CustomerID，CustomerName，CustomerAddr，CustomerCity）

能给个案例代码吗？如何实现关联查询?
比如我要查询属于订单ID1的顾客信息。求tp代码

题主的问题提得比较模糊，没有给出两张表的数量级以及order表和cumstomer表的关系（是一对多还是多对多），这里给出几点建议吧（以mysql作为数据库软件，以下都此为基础）：

多表查询的效率和所选用的数据库软件，表数据量级，业务的使用场景，查询方法等都有关系，在考虑效率之前，我们可以先问自己：在现有的业务场景以及表数据量级下，最简单的多表关联查询（join方式）效率是否已经满足需求？如果答案是肯定的话，就不要过度设计了。
当多表关联查询（join方式）效率无法满足业务需求时，常见的方法有：分成两次单表查询，优点：不会引起锁表和使用临时表，缺点：实现逻辑教复杂;order表冗余部分customer表数据，优点：多表查询问题简化为单表查询，缺点：数据有冗余以及更新逻辑复杂。

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