在MongoDB中查詢數組中的嵌入式文檔

Question

我將此子文檔嵌入到數組中：

 company:{
    products:[
      { vehicle: "Toyota", Model: "Camry" },
      { vehicle: "Honda", Model: "Civic" },
      { vehicle: "Honda", Model: "Accord" },
      { vehicle: "Mercedes", Model: "vboot" },
    ]
 }

如何選擇僅匹配的車輛

{vehicle:'Honda', Model:'Civic'}

從而：

company:{
    products:[         
      { vehicle: "Honda", Model: "Civic" },
    ]
 }

Answer 1

給定這樣的文檔：

{
    "_id" : ....,
    "company" : [ 
        {
            "vehicle" : "Toyota",
            "Model" : "Camry"
        }, 
        {
            "vehicle" : "Honda",
            "Model" : "Civic"
        }, 
        {
            "vehicle" : "Honda",
            "Model" : "Accord"
        }, 
        {
            "vehicle" : "Mercedes",
            "Model" : "vboot"
        }
    ]
}

以下查詢使用$elemMatch 查詢運算符僅查找具有vehicle:'Honda' and Model:'Civic'那些文檔：

db.collection.find(
    { company: { $elemMatch: { vehicle: 'Honda', Model: 'Civic' } } }
)

如果您只想返回公司數組中具有vehicle:'Honda' and Model:'Civic'的第一個元素vehicle:'Honda' and Model:'Civic' ，則應使用$elemMatch 投影運算符 ：

db.collection.find(
    // only find documents which have a company entry having vehicle=Honda and model=Civic
    { company: { $elemMatch: { vehicle: 'Honda', Model: 'Civic' } } }, 

    // for the documents found by the previous clause, only return the first element
    // in the company array which has vehicle=Honda and model=Civic
    { company: { $elemMatch: { vehicle: 'Honda', Model: 'Civic' } } }
)

// returns:

{
    "_id" : ObjectId("5a79613f85c9cec3a82c902c"),
    "company" : [ 
        {
            "vehicle" : "Honda",
            "Model" : "Civic"
        }
    ]
}

從文檔：

• $elemMatch查詢運算子 ...

$elemMatch運算符匹配包含一個數組字段的文檔，該數組字段的至少一個元素與所有指定的查詢條件匹配。

• $elemMatch投影運算符 ...

$elemMatch運算符將查詢結果中<array>字段的內容限制為僅包含與$elemMatch條件匹配的第一個元素。

Answer 2

find()關鍵字需要用於特定元素：

db.company.find({vehicle:"Honda",Model:"Civic"})