從表定義一對多關聯 · thinkphp5

       banner（主表）                 **banner_item（從表）**                   img（主表） ![](https://img.kancloud.cn/e7/a9/e7a97a5794f54d4aad047f6d89a73b73_160x110.png) ![](https://img.kancloud.cn/85/ef/85ef771a4f89f6feb7f371f8bfd2b79f_199x111.png) ![](https://img.kancloud.cn/09/9f/099f640b69857b39d2d3aa0bc1eb7345_216x113.png) banner_item(從表) VS img(主表)? ? ? ? **一對一** ? ? （belongsTo，它也是多對一）? ? 這里用hasOne會報錯因為外鍵在banner\_item banneritem(從表) VS banner(主表) 相對關聯 ? ? **多對一** ? ? （從表中多個項同時包含一個主表的項）（belongsTo） ![](https://img.kancloud.cn/be/90/be90f07083ed7a7c7bcbac86b8d60030_465x98.png) >[info] **從表建立多對一關聯關系** >belongsTo('關聯主表模型名','從表外鍵名','關聯表主表鍵名',\['模型別名定義'\],'join類型'); >返回belongsTo類對象 BannerItem.php Banner和Image兩個為空模型，這里就不列出了 ``` <?php namespace app\index\model; use think\Model; use think\Db; class BannerItem extends Model{ public function itemRelationBanner(){ return $this->belongsTo('Banner','banner_id','id'); } public function image(){ return $this->belongsTo('img','img_id','id'); } } ``` ## **關聯查詢** ``` $a=\app\index\model\BannerItem::get(1); echo $a->itemRelationBanner;//或者$a->item_relation_banner;都行 echo $a->item_relation_banner->des; $res1=$a->toArray(); //不推薦動態獲取關聯表數據，它每次獲取關聯對象（如：$user->itemRelationBanner）的時候就會進行實際的關聯查詢，他會進行多次查詢 //但可以使用預載入查詢來提高查詢性能，對于一對一關聯來說，只需要進行一次查詢即可獲取關聯對象數據 $b=\app\index\model\BannerItem::get(1,['itemRelationBanner', 'image']); $res2=$b->toArray(); $c=\app\index\model\BannerItem::with(['item_relation_banner', 'image'])->find(1); $res3=$c->toArray(); //查詢多條 $d=\app\index\model\BannerItem::with(['item_relation_banner', 'image'])->select(); $d=\app\index\model\BannerItem::All([],['item_relation_banner', 'image']); $res4=collection($d)->toArray(); dump($res1); dump($res2); dump($res3); dump($res4); ``` ![](https://img.kancloud.cn/95/dc/95dc3df16c1861d5c9409f1c322a14e2_384x416.png) ![](https://img.kancloud.cn/97/4d/974d8f02b99212f09d59491df367e259_334x437.png) 只是查詢當前模型查詢關聯模型的數據的話可以直接調用關聯方法 ``` $a=\app\index\model\BannerItem::get(1); $res5=$a->itemRelationBanner()->select(); //相當于："SELECT * FROM `banner` WHERE `id` = 1" $res5=$a->itemRelationBanner()->find(); //相當于："SELECT * FROM `banner` WHERE `id` = 1 LIMIT 1" dump($res5->toArray()); ``` ![](https://img.kancloud.cn/64/12/64120d41ab861c28c18aae9e795d8800_222x100.png) ``` $a= new \app\index\model\BannerItem(); $res5=$a->itemRelationBanner()->select();//"SELECT * FROM `banner`" dump($res5->toArray()); ``` ![](https://img.kancloud.cn/0f/50/0f50671a4b7e171511fe61e0993b6fa4_169x190.png) 帶條件查詢 ``` $res5=\app\index\model\BannerItem::hasWhere('image',['path'=>'/public/img/3.jpg'])->where(['banner_id'=>1])->select(); sql： "SELECT `BannerItem`.* FROM `banner_item` `BannerItem` INNER JOIN `img` `Img` ON `BannerItem`.`img_id`=`Img`.`id` WHERE `Img`.`path` = '/public/img/3.jpg' AND `banner_id` = 1" ``` ## **關聯新增**