从MongoDB中的嵌套对象结构访问对象
使用点表示法访问对象。首先让我们创建一个包含文档的集合
> db.nestedObjectDemo.insertOne({"Student" : { "StudentDetails" : { "StudentPersonalDetails" : { "StudentName" : [ "John" ],
... "StudentCountryName" : [ "US" ],
... "StudentCoreSubject" : [ "C", "Java" ],
... "StudentProject" : [ "Online Book Store", "Pig Dice Game" ] } } } });
{
"acknowledged" : true,
"insertedId" : ObjectId("5c99dfc2863d6ffd454bb650")
}以下是在find()方法的帮助下显示集合中所有文档的查询
> db.nestedObjectDemo.find().pretty();
这将产生以下输出
{
"_id" : ObjectId("5c99dfc2863d6ffd454bb650"),
"Student" : {
"StudentDetails" : {
"StudentPersonalDetails" : {
"StudentName" : [
"John"
],
"StudentCountryName" : [
"US"
],
"StudentCoreSubject" : [
"C",
"Java"
],
"StudentProject" : [
"Online Book Store",
"Pig Dice Game"
]
}
}
}
}以下是使用点表示法访问嵌套对象的查询
>db.nestedObjectDemo.find({"Student.StudentDetails.StudentPersonalDetails.StudentName":"John"}).pretty();这将产生以下输出
{
"_id" : ObjectId("5c99dfc2863d6ffd454bb650"),
"Student" : {
"StudentDetails" : {
"StudentPersonalDetails" : {
"StudentName" : [
"John"
],
"StudentCountryName" : [
"US"
],
"StudentCoreSubject" : [
"C",
"Java"
],
"StudentProject" : [
"Online Book Store",
"Pig Dice Game"
]
}
}
}
}