如何使 $elemMatch 为芒果查询中的 json 数组数据工作？

Question

我的应用程序中有一个如下所示的字段。

{
 "Ct": "HH",
  Val:{
   "Count":"A",
   "Branch":"A"
  }
 }

当我尝试在 CouchDB 中使用以下命令检索此记录时，我无法检索记录。

{
 "selector" : {
    "Val":{
      "$elemMatch":{
         "Count":"A"
       }
     }
 }

Answer 1

来自 CouchDB 文档，$elemMatch^[1]

Matches and returns all documents that contain an array field with at least one element that matches all the specified query criteria.

Val.Count 不是数组字段，因此 $elemMatch 不合适。

考虑有关子字段查询的 CouchDB 文档^[2]:

1.3.6.1.3. Subfields

A more complex selector enables you to specify the values for field of nested objects, or subfields. For example, you might use a standard JSON structure for specifying a field and subfield.

Example of a field and subfield selector, using a standard JSON structure:
{
    "imdb": {
        "rating": 8
    }
}
An abbreviated equivalent uses a dot notation to combine the field and subfield names into a single name.
{
    "imdb.rating": 8
}

具体来说，

selector: {
   "Val.Count": "A"       
}

¹ CouchDB: 1.3.6.1.7. Combination Operators
² CouchDB: 1.3.6.1.3. Subfields

如何使 $elemMatch 为芒果查询中的 json 数组数据工作？

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