Firebase查询不允许订购多个属性？ [英] Firebase query does not allow order on multiple properties?

问题描述

我试图从firebase中获取一些数据。在我的对象中，我有

pre $最近
| _UniversitId
| _objectiId1
| | _ userId：1
| | _ timestamp：143242344
| _objectiId2
| _ userId：1
| _ timestamp：143243222

我的查询路径是 http://firbasedbname.com/Recent/UniversityId 。我需要获取userId id等于1的条目，并按照时间戳设置。我尝试了以下内容：

$ $ $ $ $ $ $ $ $ $ $ $ $ $ $ $ $ $ $ $ $ $ $ ;

这会正确提取我的用户。但有没有一种可能的方式来订购这个时间戳集。要做到这一点，我试着把另一个 queryOrderedByChild 。但它说只能使用一次。我怎样才能解决这个问题？

解决方案

queryOrderedByChild只能使用一次。
解决方法将是

  | _objectiId1 
 | | _ userId：1 
 | | _时间戳：143242344 
 | | _ userId_timestamp：1_143242344 
 | _objectiId2 
 | _ userId：1 
 | _ timestamp：143243222 
 | _ userId_timestamp：1_143243222 
  

然后试试：

  FIRDatabaseQuery * query = [[ firebase queryOrderedByChild：@userId_timestamp] queryEqualToValue：@1_143242344]; 
  

检查 https://youtu.be/sKFLI5FOOHs?t=541

---

另一种方式这样做是：

pre code $ | bob $ | b $ | $ userId1：
| | _ objectId11：143242344
| | _ objectId12：143243222
| _ userId2：

然后
查询路径是 http://firbasedbname.com/Recent/UniversityId/userId1

然后按价值排序

I'm trying to fetch some data from firebase. In my object, I have

Recent
   |_UniversitId
       |_objectiId1
       |  |_ userId:1
       |  |_ timestamp:143242344
       |_objectiId2
          |_ userId:1
          |_ timestamp:143243222

My querying path is http://firbasedbname.com/Recent/UniversityId. I need to fetch the entries which are userId id is equal to 1 and order that set by timestamp. I tried the following,

FIRDatabaseQuery *query = [[firebase queryOrderedByChild:@"userId"] queryEqualToValue:@"1"];

This fetches my the users correctly. But is there a possible way to order this set by timestamp. To do that I tried by putting another queryOrderedByChild. But it says it can be used only one time. How may I fix this?

解决方案

queryOrderedByChild can be used only once. a workaround would be

   |_objectiId1
   |  |_ userId:1
   |  |_ timestamp:143242344
   |  |_ userId_timestamp:1_143242344
   |_objectiId2
      |_ userId:1
      |_ timestamp:143243222
      |_ userId_timestamp:1_143243222

Then try :

FIRDatabaseQuery *query = [[firebase queryOrderedByChild:@"userId_timestamp"] queryEqualToValue:@"1_143242344"];

check this out https://youtu.be/sKFLI5FOOHs?t=541

---

another way to do it would be :

 |_objectiId1
       |_ userId1:
       |      |_ objectId11:143242344
       |      |_ objectId12:143243222
       |_ userId2:    

Then querying path is http://firbasedbname.com/Recent/UniversityId/userId1

and then order by value

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