Question

我是mongoDB的新手，我无法弄清楚如何从集合中的对象中提取少量字段。我有一个名为recipe的集合，如下所示： -

<ListView x:Name="listView" ItemsSource="{x:Bind vm.Tables}">
    <ListView.ItemTemplate>
        <DataTemplate x:DataType="mdl:TableInfo">
            <TextBlock Text="{x:Bind Name}" FontSize="25" />
        </DataTemplate>
    </ListView.ItemTemplate>
</ListView>
<ListView x:Name="listViewTable" 
          ItemsSource="{Binding ElementName=listView, Path=SelectedItem.Fields}">
   <ListView.ItemTemplate>
      <DataTemplate x:DataType="mdl:FieldInfo">
          <TextBlock Text="{x:Bind Name}" FontSize="25" />
      </DataTemplate>
   </ListView.ItemTemplate>
</ListView>

我想在访问给定路线时仅提取两个食谱的标题和ID。目前，我正在使用这个函数，它返回两个食谱的所有字段。

[
  {
    "_id": "b44e864d-de8f-4110-b676-bbee13417b2e",
    "title": "Fried Eggs",
    "ingredients": [
      {
        "name": "Eggs",
        "amount": "10"
      },
      {
        "name": "Olive Oil",
        "amount": "2 tbs"
      }
    ],
    "steps": [
      "1. Heat the pan",
      "2.Add Olive Oil",
      "3. Add Eggs",
      "4. Saute"
    ],
    "comments": [
      {
        "_id": "8604e67c-2426-4742-bc91-25ee1c4064b5",
        "poster": "Ron Swanson",
        "comment": "Wrong instructions, Got stuck in Toaster"
      },
      {
        "_id": "040412bc-9046-49ca-9a65-19151b32cd91",
        "poster": "Tom Haverford",
        "comment": "What are Eggs?"
      },
      {
        "_id": "1034f082-b802-4382-be3e-ef50f07a530a",
        "poster": "Andy Dwyer",
        "comment": "What came  firsst, Eggs or Chicken"
      }
    ]
  },
  {
    "_id": "da6f9798-6547-42f5-85ed-043efabeb196",
    "title": "Boiled Eggs",
    "ingredients": [
      {
        "name": "Eggs",
        "amount": "5"
      },
      {
        "name": "Water",
        "amount": "3 Cups"
      }
    ],
    "steps": [
      "1.Boil the Water",
      "2.Add Eggs",
      "3. Keepit for 5 mins",
      "4. Let it Cool Down",
      "5. Peel off the shell"
    ],
    "comments": [
      {
        "_id": "cc569ebb-1307-499a-b9ee-7b24e557859f",
        "poster": "Ron Swanson",
        "comment": "Wrong instructions, Got stuck in Oven"
      },
      {
        "_id": "4f02756a-6e1b-4bda-a928-b3c5e03b55d8",
        "poster": "Leslie Knope",
        "comment": "What are Eggs?"
      },
      {
        "_id": "0f34a5cc-ebe3-41b5-8f0b-6d1a3c206e6b",
        "poster": "Andy Dwyer",
        "comment": "Can I remove the shell first and then boil?"
      }
    ]
  }]

我应该使用什么查询来提取两个食谱的标题和ID而不是所有细节？

Answer 1

根据我的理解，您正在尝试从mongo集合中获取特定字段。您只需使用投影即可实现此目的。

VariableNode

有关更多信息，请按以下步骤操作 https://docs.mongodb.com/v3.2/tutorial/project-fields-from-query-results/#return-the-specified-fields-and-the-id-field-only

从mongodb中的对象中提取一些字段

1 个答案: