Firebase 按日期字符串查询 [英] Firebase query by date string

问题描述

我知道可以按上一个问题中的时间戳进行查询，但是，如果日期采用以下格式会怎样:

I know that it's possible to query by timestamp as seen in previous question, However, what if the date is in the following format:

{
  "lambeosaurus": {
     "date" : "2012-20-03",
     "length" : 12.5,
     "weight": 5000
  },
 "stegosaurus": {
     "date" : "2015-25-13",
     "length" : 9,
     "weight" : 2500
  }
}

我将如何按日期查询?

推荐答案

您已将日期存储为字符串.当 Firebase 订购字符串时，它使用字典顺序.按照这个顺序，"2012-20-03" 在 "2012-25-01" 之前.

You've stored your dates as strings. When Firebase order strings it uses lexicographic ordering. In that order, "2012-20-03" comes before "2012-25-01".

这就是为什么您链接到的问题(以及 Firebase 文档)通常将日期存储为时间戳.那些有关于日期的所有信息，在一个单一的数字，保证正确订购.

This is the reason why the question you linked to (and the Firebase documentation) usually store dates as timestamps. Those have all the information about the date, in a single number that is guaranteed to be ordered correctly.

或者，您可以将日期存储为字符串.但在这种情况下，您必须确保日期的格式也能按字典顺序正确排序.对于您的示例:"2012-01-25" 和 "2012-03-20".

Alternatively, you can store the date as a string. But in that case you have to make sure the date is in a format that will lexicographically order correctly too. For your sample that would be: "2012-01-25" and "2012-03-20".

因此，在这种情况下，您唯一的选择是将数据结构更改为原始问题(和文档)中的数据结构，或更改为按您想要的顺序排序的字符串格式.

So in this case your only option is to change the data structure to either what was in the original question (and documentation) or to a string format that orders in the order you want.

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