如何访问MongoDB查询中的子文档？
要访问MongoDB中的子文档，请使用find()点符号。让我们创建一个包含文档的集合-
> db.demo670.insertOne({
... id:101,
... "details":
... {
... Name:"Chris",
... Age:21,
... CountryName:"US",
... SubjectName:"MongoDB"
... }
... }
... );
{
"acknowledged" : true,
"insertedId" : ObjectId("5ea3e31d04263e90dac943de")
}
> db.demo670.insertOne({ id:102, "details": { Name:"David", Age:22, CountryName:"UK", SubjectName:"MySQL" } } );
{
"acknowledged" : true,
"insertedId" : ObjectId("5ea3e33604263e90dac943df")
}在find()方法的帮助下显示集合中的所有文档-
> db.demo670.find();
这将产生以下输出-
{ "_id" : ObjectId("5ea3e31d04263e90dac943de"), "id" : 101, "details" : { "Name" : "Chris", "Age" : 21, "CountryName" : "US", "SubjectName" : "MongoDB" } }
{ "_id" : ObjectId("5ea3e33604263e90dac943df"), "id" : 102, "details" : { "Name" : "David", "Age" : 22, "CountryName" : "UK", "SubjectName" : "MySQL" } }以下是访问子文档的查询-
> db.demo670.find({"details.SubjectName":"MongoDB"},{"details.CountryName":1});7这将产生以下输出-
{ "_id" : ObjectId("5ea3e31d04263e90dac943de"), "details" : { "CountryName" : "US" } }