两种 SQL 连接表示法之间有什么区别?

What#39;s the difference between the two SQL join notations?(两种 SQL 连接表示法之间有什么区别?)

问题描述

SQL 1: select * from t1 join t2 on t1.f1 = t2.f2

SQL 2: select * from t1,t2 where t1.f1 = t2.f2

它们返回的结果是一样的.它们之间有什么区别吗?例如，在 DBMS 中如何运行它们，或者在查询计划中?

The results that they return are same. Are there any differences between them? For example, in how the DBMS runs them, or in the query plan?

推荐答案

这两个查询在操作上没有区别.

There is no operational difference between the two queries.

然而，显式连接符号是更好的学习和使用风格；将另一个留给(尚未更改的)遗留代码.

However, the explicit join notation is the better style to learn and use; leave the other for (as yet unchanged) legacy code.

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