MongoDB查询以访问数组中的对象
要访问数组中的对象，请使用点表示法。让我们创建一个包含文档的集合-
> db.demo299.insertOne(
... {
... "id":100,
... "Name":"Robert",
... "details":[
... {
... "SubjectName":["C++","Python"]
... },
... {
... "SubjectName":["Spring","Hibernate"]
... }
... ]
... }
...);
{
"acknowledged" : true,
"insertedId" : ObjectId("5e4d685a5d93261e4bc9ea4b")
}
>
>
> db.demo299.insertOne(
... {
... "id":101,
... "Name":"Adam",
... "details":[
... {
... "SubjectName":["Python","JSP"]
... },
... {
... "SubjectName":["Servlet","Operating System"]
... }
... ]
... }
...);
{
"acknowledged" : true,
"insertedId" : ObjectId("5e4d685b5d93261e4bc9ea4c")
}在find()方法的帮助下显示集合中的所有文档-
> db.demo299.find();
这将产生以下输出-
{
"_id" : ObjectId("5e4d685a5d93261e4bc9ea4b"), "id" : 100, "Name" : "Robert", "details" : [
{ "SubjectName" : [ "C++", "Python" ] },
{ "SubjectName" : [ "Spring", "Hibernate" ] }
]
}
{
"_id" : ObjectId("5e4d685b5d93261e4bc9ea4c"), "id" : 101, "Name" : "Adam", "details" : [
{ "SubjectName" : [ "Python", "JSP" ] }, { "SubjectName" : [ "Servlet", "Operating System" ] }
]
}以下是访问数组中对象的查询-
> db.demo299.find({"details.SubjectName":"Servlet"});这将产生以下输出-
{
"_id" : ObjectId("5e4d685b5d93261e4bc9ea4c"), "id" : 101, "Name" : "Adam", "details" : [
{ "SubjectName" : [ "Python", "JSP" ] }, { "SubjectName" : [ "Servlet", "Operating System" ] }
]
}