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
社会研究
时尚研究
法律研究如何从 MongoDB 集合中检索所有嵌套字段？
为此，请使用 aggregate()。让我们使用文档创建集合——
>db.demo138.insertOne({"Id":101,"PlayerDetails":[{"PlayerName":"Chris","PlayerScore":400},{"PlayerName":"David","PlayerScore":1000}]});
{
"acknowledged" : true,
"insertedId" : ObjectId("5e31bb9ffdf09dd6d08539a1")
}
>db.demo138.insertOne({"Id":102,"PlayerDetails":[{"PlayerName":"Bob","PlayerScore":500},{"PlayerName":"Carol","PlayerScore":600}]});
{
"acknowledged" : true,
"insertedId" : ObjectId("5e31bbcefdf09dd6d08539a2")
}使用 find() 方法显示集合中的所有文档——
> db.demo138.find();
这将生成以下输出——
{
"_id" : ObjectId("5e31bb9ffdf09dd6d08539a1"), "Id" : 101, "PlayerDetails" : [
{ "PlayerName" : "Chris", "PlayerScore" : 400 },
{ "PlayerName" : "David", "PlayerScore" : 1000 }
]
}
{
"_id" : ObjectId("5e31bbcefdf09dd6d08539a2"), "Id" : 102, "PlayerDetails" : [
{ "PlayerName" : "Bob", "PlayerScore" : 500 }, { "PlayerName" : "Carol", "PlayerScore" : 600 }
]
}以下是检索集合中所有嵌套字段的查询——
> db.demo138.aggregate([{ $unwind:"$PlayerDetails" }, { $project: { "PlayerName":"$PlayerDetails.PlayerName", "PlayerScore":"$PlayerDetails.PlayerScore" } } ] );这将生成以下输出——
{ "_id" : ObjectId("5e31bb9ffdf09dd6d08539a1"), "PlayerName" : "Chris", "PlayerScore" : 400 }
{ "_id" : ObjectId("5e31bb9ffdf09dd6d08539a1"), "PlayerName" : "David", "PlayerScore" : 1000 }
{ "_id" : ObjectId("5e31bbcefdf09dd6d08539a2"), "PlayerName" : "Bob", "PlayerScore" : 500 }
{ "_id" : ObjectId("5e31bbcefdf09dd6d08539a2"), "PlayerName" : "Carol", "PlayerScore" : 600 }
更新于： 31-Mar-2020
863 浏览
广告