摘要： 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=44917SQL: difference between inner and outer joinhttp://stackoverflow.com/questions/38549/sql-difference-between-inner-and-outer-join 阅读全文