如何在MongoDB中订购列表并将位置添加到其项目中？
sort()。让我们创建一个包含文档的集合-> db.demo581.insertOne({"Name":"Chris","Score":56});{
"acknowledged" : true, "insertedId" : ObjectId("5e91cbbbfd2d90c177b5bcb6")
}
> db.demo581.insertOne({"Name":"Bob","Score":240});{
"acknowledged" : true, "insertedId" : ObjectId("5e91cbbbfd2d90c177b5bcb7")
}
> db.demo581.insertOne({"Name":"David","Score":150});{
"acknowledged" : true, "insertedId" : ObjectId("5e91cbbcfd2d90c177b5bcb8")
}在find()方法的帮助下显示集合中的所有文档-
> db.demo581.find();
这将产生以下输出-
{ "_id" : ObjectId("5e91cbbbfd2d90c177b5bcb6"), "Name" : "Chris", "Score" : 56 }
{ "_id" : ObjectId("5e91cbbbfd2d90c177b5bcb7"), "Name" : "Bob", "Score" : 240 }
{ "_id" : ObjectId("5e91cbbcfd2d90c177b5bcb8"), "Name" : "David", "Score" : 150 }以下是查询列表顺序并将其位置添加到MongoDB中的项目的查询-
> db.demo581.createIndex({Score:1})
{
"createdCollectionAutomatically" : false,
"numIndexesBefore" : 1,
"numIndexesAfter" : 2,
"ok" : 1
}
> var i = 1;
> db.demo581.find().sort({"Score": 1}).forEach(function (d){
... d.Position = i;
... i++;
... db.demo581.save(d);
... })在find()方法的帮助下显示集合中的所有文档-
> db.demo581.find();
这将产生以下输出-
{ "_id" : ObjectId("5e91cbbbfd2d90c177b5bcb6"), "Name" : "Chris", "Score" : 56, "Position" : 1 }
{ "_id" : ObjectId("5e91cbbbfd2d90c177b5bcb7"), "Name" : "Bob", "Score" : 240, "Position" : 3 }
{ "_id" : ObjectId("5e91cbbcfd2d90c177b5bcb8"), "Name" : "David", "Score" : 150, "Position" : 2 }