MongoDB按子字段查询？
您可以使用点（。）表示法按子字段进行查询。让我们用文档创建一个集合。使用文档创建集合的查询如下-
> db.queryBySubFieldDemo.insertOne(
... {
... "StudentPersonalDetails" : {"StudentName" : "John","StudentHobby" :"Photography"},
... "StudentScores" : {"MathScore" : 56}
... }
... );
{
"acknowledged" : true,
"insertedId" : ObjectId("5c92c2995259fcd195499808")
}
> db.queryBySubFieldDemo.insertOne(
... {
... "StudentPersonalDetails" : {"StudentName" : "Chris","StudentHobby" :"Reading"},
... "StudentScores" : {"MathScore" : 97}
... }
... );
{
"acknowledged" : true,
"insertedId" : ObjectId("5c92c2df5259fcd195499809")
}在find()method的帮助下显示集合中的所有文档。查询如下-
> db.queryBySubFieldDemo.find().pretty();
以下是输出-
{
"_id" : ObjectId("5c92c2995259fcd195499808"),
"StudentPersonalDetails" : {
"StudentName" : "John",
"StudentHobby" : "Photography"
},
"StudentScores" : {
"MathScore" : 56
}
}
{
"_id" : ObjectId("5c92c2df5259fcd195499809"),
"StudentPersonalDetails" : {
"StudentName" : "Chris",
"StudentHobby" : "Reading"
},
"StudentScores" : {
"MathScore" : 97
}
}这是按子字段查询-
> db.queryBySubFieldDemo.find({"StudentPersonalDetails.StudentName":"Chris"}).pretty();以下是输出-
{
"_id" : ObjectId("5c92c2df5259fcd195499809"),
"StudentPersonalDetails" : {
"StudentName" : "Chris",
"StudentHobby" : "Reading"
},
"StudentScores" : {
"MathScore" : 97
}
}