Firebase如何读取数值直到指定长度。

huangapple
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英文:

firebase how to read values until specified length

问题

I want to get the total number count until specified.

this is my database: database picture

I want to count where ticket_status is not served

ex: I want to count until A6, I will count A1 until A5 where the value of ticket_status is not served. so the final count will be 3.

is there any filtering kind?

I have this code but it just counts all nodes with the value of "not served"

  1. dbref.child("Queue").child(a.value.toString()).orderByChild("ticket_status").equalTo("not served").addValueEventListener(object : ValueEventListener{
  2.     override fun onDataChange(snap: DataSnapshot) {
  3.         val count = snap.childrenCount
  4.         dbref.child("Student_Queue_Reserve").child(idNumber.toString()).child("people_ahead").setValue((count-1).toString())
  5.     }
  6.     override fun onCancelled(error: DatabaseError) {
  7.     }
  8. })
英文:

I want to get the total number count until specified.

this is my database: database picture

I want to count where ticket_status is not served

ex: I want to count until A6, I will count A1 until A5 where the value of ticket_status" is not served. so the final count will be 3.

is there any filtering kind?

I have this code but it just counts all nodes with the value of "not served"

  1. dbref.child("Queue").child(a.value.toString()).orderByChild("ticket_status").equalTo("not served").addValueEventListener(object : ValueEventListener{
  2.                                 override fun onDataChange(snap: DataSnapshot) {
  3.                                         val count = snap.childrenCount
  4.                               dbref.child("Student_Queue_Reserve").child(idNumber.toString()).child("people_ahead").setValue((count-1).toString())
  5.                                 }
  6.                                 override fun onCancelled(error: DatabaseError) {
  7.                                 }
  8.                             })

答案1

得分: 0

I want to count until A6, I will count A1 until A5 where the value of ticket_status is not served. So the final count will be 3.

There is no way you can do that in the Realtime Database because queries can only order/filter on a single property. There are cases in which you can combine the values you want to filter into a single property. For example, please check my answer below:

If you're allowed to change the database schema, then you should consider denormalizing the data. So a structure like below will do the trick:

  1. db
  2. |
  3. --- Queue
  4.      |
  5.      --- Accounting Office
  6.            |
  7.            --- served
  8.            |    |
  9.            |    --- A1
  10.            |    |   |
  11.            |    |   --- serving_token: "A001"
  12.            |    |   |
  13.            |    |   --- ticket_status: "served"
  14.            |
  15.            --- A2
  16.                |
  17.                --- serving_token: "A002"
  18.                |
  19.                --- ticket_status: "served"
  20.            |
  21.            --- not served
  22.                 |
  23.                 --- A3
  24.                 |   |
  25.                 |   --- serving_token: "A003"
  26.                 |   |
  27.                 |   --- ticket_status: "not served"
  28.                 |
  29.                 --- A4
  30.                 |   |
  31.                 |   --- serving_token: "A004"
  32.                 |   |
  33.                 |   --- ticket_status: "not served"
  34.                 |
  35.                 --- A5
  36.                 |   |
  37.                 |   --- serving_token: "A005"
  38.                 |   |
  39.                 |   --- ticket_status: "not served"
  40.                 |
  41.                 --- A6
  42.                     |
  43.                     --- serving_token: "A006"
  44.                     |
  45.                     --- ticket_status: "not served"

Now you can query the "not served" node, using a combination of Query#orderByKey() and Query#endAt(java.lang.String).

英文:

> I want to count until A6, I will count A1 until A5 where the value of ticket_status" is not served. So the final count will be 3.

There is no way you can do that in the Realtime Database because queries can only order/filter on a single property. There are cases in which you can combine the values you want to filter into a single property. For example, please check my answer below:

If you're allowed to change the database schema, then you should consider denormalizing the data. So a structure like below will do the trick:

  1. db
  2. |
  3. --- Queue
  4.      |
  5.      --- Accounting Office
  6.            |
  7.            --- served
  8.            |    |
  9.            |    --- A1
  10.            |    |   |
  11.            |    |   --- serving_token: "A001"
  12.            |    |   |
  13.            |    |   --- ticket_status: "served"
  14.            |    |
  15.            |    --- A2
  16.            |        |
  17.            |        --- serving_token: "A002"
  18.            |        |
  19.            |        --- ticket_status: "served"
  20.            |
  21.            --- not served
  22.                 |
  23.                 --- A3
  24.                 |   |
  25.                 |   --- serving_token: "A003"
  26.                 |   |
  27.                 |   --- ticket_status: "not served"
  28.                 |
  29.                 --- A4
  30.                 |   |
  31.                 |   --- serving_token: "A004"
  32.                 |   |
  33.                 |   --- ticket_status: "not served"
  34.                 |
  35.                 --- A5
  36.                 |   |
  37.                 |   --- serving_token: "A005"
  38.                 |   |
  39.                 |   --- ticket_status: "not served"
  40.                 |
  41.                 --- A6
  42.                     |
  43.                     --- serving_token: "A006"
  44.                     |
  45.                     --- ticket_status: "not served"

Now you can query the "not served" node, using a combination of Query#orderByKey() and Query#endAt(java.lang.String)

  1. db.child("Queue").child("Accounting Office").child("not served").orderByKey().endAt("A6");

答案2

得分: 0

你可以尝试这种方法，不需要查询：

  1. ArrayList servedArray;
  2. ArrayList notServedArray;
  • 获取数据快照
  • 循环遍历快照
  • 如果值等于 "served"，则添加到 servedArray
  • 否则，如果值等于 "not served"，则添加到 notServedArray

对于计数，你可以使用：

  1. servedArray.size
  2. notServedArray.size
英文:

You can try this approach without query:

  1. ArrayList servedArray ;
  2. ArrayList notServedArray ;
  • get a data snapshot
  • loop through snapshot
  • if value == "served" >> add to servedArray
  • else if value equal == "not served" add to notServedArray

And for count you can use :

  1. servedArray.size
  2. notServedArray.size

huangapple
  • 本文由 发表于 2023年2月13日 23:22:49
  • 转载请务必保留本文链接：https://go.coder-hub.com/75437862.html
  • android
  • firebase
  • firebase-realtime-database
  • java
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