如何在MongoDB中选择特定的子文档？
要选择MongoDB中的特定子文档，请使用find()。让我们创建一个包含文档的集合-
> db.demo37.insertOne({"Details":[{"Name":"Chris","Age":21},{"Name":"David","Age":23}]});
{
"acknowledged" : true,
"insertedId" : ObjectId("5e176635cfb11e5c34d898d7")
}
> db.demo37.insertOne({"Details":[{"Name":"Sam","Age":23},{"Name":"Robert","Age":25}]});
{
"acknowledged" : true,
"insertedId" : ObjectId("5e17664acfb11e5c34d898d8")
}在find()方法的帮助下显示集合中的所有文档-
> db.demo37.find();
这将产生以下输出-
{ "_id" : ObjectId("5e176635cfb11e5c34d898d7"), "Details" : [ { "Name" : "Chris", "Age" : 21 }, { "Name" : "David", "Age" : 23 } ] }
{ "_id" : ObjectId("5e17664acfb11e5c34d898d8"), "Details" : [ { "Name" : "Sam", "Age" : 23 }, { "Name" : "Robert", "Age" : 25 } ] }以下是选择子文档的查询-
> db.demo37.find({'Details.Name' : 'Sam'},{_id: 0, 'Details.$.Name': 1});这将产生以下输出-
{ "Details" : [ { "Name" : "Sam", "Age" : 23 } ] }