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# 视图查询 视图查询可以实现不依赖数据库视图的多表查询,并不需要数据库支持视图,是JOIN方法的推荐替代方法,例如: ``` Db::view('User', 'id,name') ->view('Profile', 'truename,phone,email', 'Profile.user_id=User.id') ->view('Score', 'score', 'Score.user_id=Profile.id') ->where('score', '>', 80) ->select(); ``` 生成的SQL语句类似于: ``` SELECT User.id,User.name,Profile.truename,Profile.phone,Profile.email,Score.score FROM think_user User INNER JOIN think_profile Profile ON Profile.user_id=User.id INNER JOIN think_socre Score ON Score.user_id=Profile.id WHERE Score.score > 80 ``` > 注意,视图查询无需调用`table`和`join`方法,并且在调用`where`和`order`方法的时候只需要使用字段名而不需要加表名。 默认使用`INNER join`查询,如果需要更改,可以使用: ``` Db::view('User', 'id,name') ->view('Profile', 'truename,phone,email', 'Profile.user_id=User.id', 'LEFT') ->view('Score', 'score', 'Score.user_id=Profile.id', 'RIGHT') ->where('score', '>', 80) ->select(); ``` 生成的SQL语句类似于: ``` SELECT User.id,User.name,Profile.truename,Profile.phone,Profile.email,Score.score FROM think_user User LEFT JOIN think_profile Profile ON Profile.user_id=User.id RIGHT JOIN think_socre Score ON Score.user_id=Profile.id WHERE Score.score > 80 ``` 可以使用别名: ``` Db::view('User', ['id' => 'uid', 'name' => 'account']) ->view('Profile', 'truename,phone,email', 'Profile.user_id=User.id') ->view('Score', 'score', 'Score.user_id=Profile.id') ->where('score', '>', 80) ->select(); ``` 生成的SQL语句变成: ``` SELECT User.id AS uid,User.name AS account,Profile.truename,Profile.phone,Profile.email,Score.score FROM think_user User INNER JOIN think_profile Profile ON Profile.user_id=User.id INNER JOIN think_socre Score ON Score.user_id=Profile.id WHERE Score.score > 80 ``` 可以使用数组的方式定义表名以及别名,例如: ``` Db::view(['think_user' => 'member'], ['id' => 'uid', 'name' => 'account']) ->view('Profile', 'truename,phone,email', 'Profile.user_id=member.id') ->view('Score', 'score', 'Score.user_id=Profile.id') ->where('score', '>', 80) ->select(); ``` 生成的SQL语句变成: ``` SELECT member.id AS uid,member.name AS account,Profile.truename,Profile.phone,Profile.email,Score.score FROM think_user member INNER JOIN think_profile Profile ON Profile.user_id=member.id INNER JOIN think_socre Score ON Score.user_id=Profile.id WHERE Score.score > 80 ```