数据结构
网络
RDBMS
操作系统
Java
MS Excel
iOS
HTML
CSS
Android
Python
C 编程
C++
C#
MongoDB
MySQL
Javascript
PHP
物理
化学
生物
数学
英语
经济学
心理学
社会学
时装学
法学Group query upon nested object in MongoDB?
为此，在 MongoDB 中，使用点符号以及 $group 。让我们使用文档创建一个集合 -
> db.demo617.insertOne(
... {
...
... "clientDetails": {
... "Name": "Chris",
... "Age":32,
... "Project":"Online Library Management System"
... }
... }
... );
{
"acknowledged" : true,
"insertedId" : ObjectId("5e99d2b86c954c74be91e69b")
}
>
> db.demo617.insertOne(
... {
...
... "clientDetails": {
... "Name": "David",
... "Age":34,
... "Project":"Online Hospital Management System"
... }
... }
... );
{
"acknowledged" : true,
"insertedId" : ObjectId("5e99d2b86c954c74be91e69c")
}
>
> db.demo617.insertOne(
... {
...
... "clientDetails": {
... "Name": "David",
... "Age":34,
... "Project":"Online Library Management System"
... }
... }
... );
{
"acknowledged" : true,
"insertedId" : ObjectId("5e99d2b96c954c74be91e69d")
}在集合中显示所有文档，使用 find() 方法 -
> db.demo617.find();
这将产生以下输出 -
{ "_id" : ObjectId("5e99d2b86c954c74be91e69b"), "clientDetails" : { "Name" : "Chris", "Age" : 32, "Project" : "Online Library Management System" } }
{ "_id" : ObjectId("5e99d2b86c954c74be91e69c"), "clientDetails" : { "Name" : "David", "Age" : 34, "Project" : "Online Hospital Management System" } }
{ "_id" : ObjectId("5e99d2b96c954c74be91e69d"), "clientDetails" : { "Name" : "David", "Age" : 34, "Project" : "Online Library Management System" } }在 MongoDB 中，对嵌套对象进行组查询 -
> db.demo617.aggregate({ $group : {_id : "$clientDetails.Project", All : { $sum : 1 }} });这将产生以下输出 -
{ "_id" : "Online Hosiptal Management System", "All" : 1 }
{ "_id" : "Online Library Management System", "All" : 2 }
更新于:2020-5-12
240 次查看
广告