PRIMARY KEY (`id`, `topic_id`)
比如我的表 包含了复合主键,其中id是自增类型,使用save方法插入数据后,无法获取id的返回值
$bao = model('Bao');
$bao->topic_id = $topic_id;
$bao->user_id = $user_id;
$bao->user_name = $user_name;
$bao->save();
$bao->id;//这里会报错:[ error ] [0]类的属性不存在:app\serve\model\Bao->id