MongoDb:$ push/$ addtoset之间的区别 [英] MongoDb: Difference between $push/$addtoset

问题描述

我阅读了MongoDb中的文档，并使用了简单的证明，但我只发现: Push正在对数组进行排序，但addtoSet不是.

I read the documentation in the MongoDb and I used a simple proves and I only look that: Push is sorting the array but addtoSet isn't it.

对我来说，视觉上是一样的，我不知道区别.

For me visually is the same, I don't know the difference.

有人可以解释一下我的区别吗?

Could anybody explain me the difference?

另一个人认为，如果它可以是西班牙语或简单的英语，我会予以保留.

Another think if it could be in spanish or in a simple english, i'll aprecite it.

推荐答案

$addToSet如果该项目已包含该项目，则不要将其添加到给定的字段中，另一方面，$push会将给定的对象添加到该字段中它存在与否.

$addToSet do not add the item to the given field if it already contains it, on the other hand $push will add the given object to field whether it exists or not.

{_id: "docId", items: [1, 2]}
db.items.update({_id:"docId"}, {$addToSet:{items: 2}}); // This won't update the document as it already contains 2
db.items.update({_id:"docId"}, {$push: {item:2}}); // this will update the document. new document {_id: "docId", items:[1,2,2]}

这篇关于MongoDb:$ push/$ addtoset之间的区别的文章就介绍到这了，希望我们推荐的答案对大家有所帮助，也希望大家多多支持IT屋！