yii框架详解 之 CActiveRecord
1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 | /** * @return array relational rules. */ public function relations() { // NOTE: you may need to adjust the relation name and the related // class name for the relations automatically generated below. return array( 'visas'=>array(self::MANY_MANY, 'Visa', '{{visa_to_order}}(id_order, id_visa)', 'select'=>array( '*', #获取所有字段 'visas_visas.price AS price_visa', #visas_visas是关系表的别名，获取关系表里的字段值 ), ), 'user'=>array(self::BELONGS_TO, 'User','id_customer)'), ); } |
Yii的relations里self::BELONGS_TO默认是用当前指定的键跟关联表的主键进行join，例如：
return array(
'reply' => array(self::BELONGS_TO, 'BookPostReply', 'postid'),
);默认生成的sql是 on id = postid，id是BookPostReply的主键。
但今天我遇到的需求却是需要生成 on BookPostReply.postid = t.postid，不去关联主键，
后来无意中看到有个on的属性，刚好跟sql里的on一样，于是抱着试试的想法，在配置里加了上去
return array(
'reply' => array(self::BELONGS_TO, 'BookPostReply', 'postid', 'on' => 't.postid=reply.postid'),
);看调试信息里的SQL语句，发现yii生成了一条 on id = postid and t.postid=reply.postid 这样的语句，看到这就已经明白这个东西的作用了，于是将postid清空，改成如下：
return array(
'reply' => array(self::BELONGS_TO, 'BookPostReply', '', 'on' => 't.postid=reply.postid'),
);其实，Yii的文档有说明： 如果你需要指定自定义的pk->fk关联，你可以定义数组（‘fk’=> ‘pk'）。
【多条件下关联查询结果集】
案例：
$this->news = News::model()->with(array(
'sites'=>array('condition'=>'sites.id_site='.Yii::app()->params['siteId'],'together'=>true),
'categories'=>array('condition'=>'categories.id_category='.$this->categoryId,'together'=>true),
))->findAll(array(
'limit'=>$this->limit,
'condition'=>'t.active=1',
'order'=>'t.position'
));
使用with('关系名称1','关系名称2')方法，将延后查询关联表，
若如上案例，在with方法中，返回关系数组，将更灵活。
若想即时联合查询，需要添加'together'=>true属性值，才会组合为一句SQL进行查询。
我们来看下CActiveRecord.php文件里，yii是如何设计with（）方法的。
/**
* Specifies which related objects should be eagerly loaded.
* This method takes variable number of parameters. Each parameter specifies
* the name of a relation or child-relation. For example,
* <pre>
* // find all posts together with their author and comments
* Post::model()->with('author','comments')->findAll();
* // find all posts together with their author and the author's profile
* Post::model()->with('author','author.profile')->findAll();
* </pre>
* The relations should be declared in {@link relations()}.
*
* By default, the options specified in {@link relations()} will be used
* to do relational query. In order to customize the options on the fly,
* we should pass an array parameter to the with() method. The array keys
* are relation names, and the array values are the corresponding query options.
* For example,
* <pre>
* Post::model()->with(array(
* 'author'=>array('select'=>'id, name'),
* 'comments'=>array('condition'=>'approved=1', 'order'=>'create_time'),
* ))->findAll();
* </pre>
*
* @return CActiveRecord the AR object itself.
*/
public function with()
{
if(func_num_args()>0)
{
$with=func_get_args();
if(is_array($with[0])) // the parameter is given as an array
$with=$with[0];
if(!empty($with))
$this->getDbCriteria()->mergeWith(array('with'=>$with));
}
return $this;
}
我们再去看 CDbCriteria 类中的 mergeWith 方法定义：
/**
* Merges with another criteria.
* In general, the merging makes the resulting criteria more restrictive.
* For example, if both criterias have conditions, they will be 'AND' together.
* Also, the criteria passed as the parameter takes precedence in case
* two options cannot be merged (e.g. LIMIT, OFFSET).
* @param mixed $criteria the criteria to be merged with. Either an array or CDbCriteria.
* @param string|boolean $operator the operator used to concatenate where and having conditions. Defaults to 'AND'.
* For backwards compatibility a boolean value can be passed:
* - 'false' for 'OR'
* - 'true' for 'AND'
*/
public function mergeWith($criteria,$operator='AND'){......}
注意，这里就是我要强调的地方，yii默认且只执行关联表之间的AND条件查询，也就是说，在给定不同条件查询时，yii只为我们求取不同条件的交集结果返回。
但是在底层的CDbCriteria 类中，预留了参数$operator给我们。有需求的同学需要重写CActiveRecord来实现拓展了哦。
