->leftJoin

 1 $query = Area::find()->andWhere([‘a.is_delete‘=>0,‘a.level‘=>4,‘a.is_open‘=>1]);
 2 
 3 $query->select(‘a.name,a.id,a.parent_id,c.name AS city_name,c.parent_id,b.name AS province_name,‘)
 4 ->alias(‘a‘)
 5 ->andWhere([‘c.level‘=>3,‘c.is_open‘=>1,‘c.is_delete‘=>0])
 6 ->leftJoin([‘c‘=>Area::tableName()],‘c.id=a.parent_id‘)
 7 ->andWhere([‘b.level‘=>2,‘b.is_open‘=>1,‘b.is_delete‘=>0])
 8 ->leftJoin([‘b‘=>Area::tableName()],‘b.id=c.parent_id‘);
 9 if ($citys) {
10 $query->andWhere([‘c.id‘=>$citys]);
11 }
12 
13 if ($provinces) {   // 这个是搜索的条件   当搜索提交数据过来是  加上where 
14 $query->andWhere([‘b.id‘=>$provinces]);
15 }
16 
17 $count = $query->count();
18 $p = new Pagination([‘totalCount‘=>$count,‘pageSize‘=>10]);  // 一页显示10条数据
19 
20 $list = $query->offset($p->offset)
21 ->limit($p->limit)
22 ->asArray()  // 转成 数组形式  ，不加的话就是以对象的形式返回 
23 ->all();
24 
25 return [$list,$p];  // list 数据 p 分页