关于 FROM a,b where a.id=b.id和 a LEFT JOIN b on a.id=b.id的区别

关于 FROM a,b where a.id=b.id和 a LEFT JOIN b on a.id=b.id的区别

 

两者是等价的, 前者是隐式的内连接.

一般用后者, sql语句看起来清晰一些.

 

明确队隐含的SQL联接
http://zh-cn.w3support.net/index.php?db=so&id=44917

SQL: difference between inner and outer join
http://stackoverflow.com/questions/38549/sql-difference-between-inner-and-outer-join