问题描述
据说我有一个这样的数据库结构
Supposedly I have a database structure like this
Person ('name', 'age')
Belonging ('person', 'type')
像这样的关系
Person -> Belongings (one to many)
我想查询所有人的物品数量，就像这样
and I want to query all person with their number of belongings included like this
Array[0] -> name, age, numberOfBelongings,
Array[1] -> name, age, numberOfBelongings,
etc
我该怎么做?我尝试使用CloudCode，但结果发现获取方法是异步的，所以我无法获取每个人的物品数量.
How do I do this? I tried to use CloudCode but, it turned out the fetching method is asynchronous, so I can't fetch the number of belongings to each person.
推荐答案
你不能直接这样做.如果您需要此计数，您可以在 Person 类(即 numberofbelongings)上创建一个字段，您可以在 Belonging 上的 afterSave 云代码挂钩中更新该字段.每当保存 Belonging 时，您还会增加 Person 对象上的 numberofbelongings 字段，并将其保存.
You can't do that directly. If you need this count, you could create a field on the Person class (i.e. numberofbelongings) which you update in an afterSave cloud code hook on Belonging. Whenever a Belonging is saved, you also increment the numberofbelongings field on the Person object, and save that as well.
没有额外的查询，没有来自您的设备的额外网络流量，并且您始终拥有可用于任何 Person 对象的计数.
No extra queries, no extra network traffic from your device, and your always have the count available for any Person object.
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