大家写sql语句,有隐式连接还是显式连接!? - PHP进阶讨论
有2个网友回答
SQL 定义了两种不同语法方式去表示"连接". 首先是"显示连接符号", 它显式地使用关键字 JOIN, 其次是"隐式连接符号", 它使用所谓的"隐式连接符号". 隐式连接符号把需要连接的表放到 SELECT 语句的 FROM 部分, 并用逗号隔开. 这样就构成了一个"交叉连接", WHERE 语句可能放置一些过滤谓词(过滤条件). 那些过滤谓词在功能上等价于显式连接符号.
显示和隐身在特殊情况下返回结果不同,参照你的目标,得视情况而定。
left join 是left outer join的简写,left join默认是outer属性的。
left join 是left outer join的简写,left join默认是outer属性的。
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