MongoDB-如何访问文档中的字段？
find()。让我们创建一个包含文档的集合-> db.demo565.insertOne(
... {
... id:101,
... Name:"David",
... "CountryName":"US"
... }
... );
{
"acknowledged" : true,
"insertedId" : ObjectId("5e90896739cfeaaf0b97b577")
}
>
> db.demo565.insertOne(
... {
... id:102,
... Name:"Carol",
... "CountryName":"UK"
... }
... );
{
"acknowledged" : true,
"insertedId" : ObjectId("5e90896839cfeaaf0b97b578")
}
>
> db.demo565.insertOne(
... {
... id:103,
... Name:"Sam",
... "CountryName":"AUS"
... }
... );
{
"acknowledged" : true,
"insertedId" : ObjectId("5e90896839cfeaaf0b97b579")
}在find()方法的帮助下显示集合中的所有文档-
> db.demo565.find();
这将产生以下输出-
{ "_id" : ObjectId("5e90896739cfeaaf0b97b577"), "id" : 101, "Name" : "David", "CountryName" : "US" }
{ "_id" : ObjectId("5e90896839cfeaaf0b97b578"), "id" : 102, "Name" : "Carol", "CountryName" : "UK" }
{ "_id" : ObjectId("5e90896839cfeaaf0b97b579"), "id" : 103, "Name" : "Sam", "CountryName" : "AUS" }以下是访问字段的查询-
> db.demo565.find({"Name":"Carol",CountryName:"UK"},{Name:1});这将产生以下输出-
{ "_id" : ObjectId("5e90896839cfeaaf0b97b578"), "Name" : "Carol" }