class  User extends CActiveRecord
class  Post extends CActiveRecord

//class Post
public function relations()
    {
        return array(
            ‘author‘=>array(self::BELONGS_TO, ‘User‘, ‘id‘)
        );
    }

// 格式为
// ‘relationsName‘ => array("relationship", "关联表", "该表的外键")
// relationName 可以随意
// relationship 为
// self::BELONGS_TO
// self::HAS_MANY
// self::HAS_ONE
// self::MANY_MANY  四个常量