从MongoDB集合中检索数据？
findOne()在MongoDB中使用。让我们创建一个包含文档的集合-> db.demo463.insertOne({"StudentName":"Chris
Brown","StudentAge":21,"StudentCountryName":"US"});{
"acknowledged" : true,
"insertedId" : ObjectId("5e7f7ec8cb66ccba22cc9dcf")
}
> db.demo463.insertOne({"StudentName":"David
Miller","StudentAge":23,"StudentCountryName":"UK"});{
"acknowledged" : true,
"insertedId" : ObjectId("5e7f7ed5cb66ccba22cc9dd0")
}
> db.demo463.insertOne({"StudentName":"John
Doe","StudentAge":22,"StudentCountryName":"AUS"});{
"acknowledged" : true,
"insertedId" : ObjectId("5e7f7ee1cb66ccba22cc9dd1")
}
> db.demo463.insertOne({"StudentName":"John
Smith","StudentAge":24,"StudentCountryName":"US"});{
"acknowledged" : true,
"insertedId" : ObjectId("5e7f7eefcb66ccba22cc9dd2")
}在find()方法的帮助下显示集合中的所有文档-
> db.demo463.find();
这将产生以下输出-
{ "_id" : ObjectId("5e7f7ec8cb66ccba22cc9dcf"), "StudentName" : "Chris Brown",
"StudentAge" : 21, "StudentCountryName" : "US" }
{ "_id" : ObjectId("5e7f7ed5cb66ccba22cc9dd0"), "StudentName" : "David Miller",
"StudentAge" : 23, "StudentCountryName" : "UK" }
{ "_id" : ObjectId("5e7f7ee1cb66ccba22cc9dd1"), "StudentName" : "John Doe", "StudentAge" :
22, "StudentCountryName" : "AUS" }
{ "_id" : ObjectId("5e7f7eefcb66ccba22cc9dd2"), "StudentName" : "John Smith", "StudentAge"
: 24, "StudentCountryName" : "US" }以下是从MongoDB检索数据的查询-
> db.demo463.findOne({"StudentName":"John Doe"});这将产生以下输出-
{
"_id" : ObjectId("5e7f7ee1cb66ccba22cc9dd1"),
"StudentName" : "John Doe",
"StudentAge" : 22,
"StudentCountryName" : "AUS"
}