在Firebase数据库中按降序排序 [英] Sorting in descending order in Firebase database

问题描述

Firebase实时数据库中有以下书籍列表:

There is this list of Books in the Firebase Realtime Database:

[
  {
    title: "Don't Make Me Think",
    upvotes: 110
  },
  {
    title: "The Mythical Man Month",
    upvotes: 111
  },
  {
    title: "Code Complete 2",
    upvotes: 112
  }
]

默认情况下，以下查询按ASC顺序返回此列表:

By default, the query below returns this list in ASC order:

firebase.database().ref('books').orderByChild('upvotes')

我该如何通过upvotes DESC查询和订购它们?

How can I query and order them by upvotes DESC instead?

推荐答案

不幸的是，firebase不允许以降序返回.我通常只是颠倒了返回客户端的结果的顺序.

Unfortunately firebase doesn't allow returning by descending order. I have generally just reversed the order of the results returned client side.

如果您的数据查询太大而无法对客户端进行排序

If your data query is too large to sort client side you can do

firebase.database().ref('books').orderByChild('ups').limitToLast(2)

，然后从那里求反.可以在此处

and then invert the results from there. Documentation can be seen here

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