在MongoDB中按子文档排序
要按子文档排序，请在MongoDB中使用$sort。让我们创建一个包含文档的集合-
> db.demo245.insertOne(
... {
... "_id": 101,
... "deatils": [
... { "DueDate": new ISODate("2019-01-10"), "Value": 45},
... {"DueDate": new ISODate("2019-11-10"), "Value": 34 }
... ]
... }
...);
{ "acknowledged" : true, "insertedId" : 101 }
> db.demo245.insertOne(
... {
... "_id": 102,
... "details": [
... { "DueDate": new ISODate("2019-12-11"), "Value": 29},
... {"DueDate": new ISODate("2019-03-10"), "Value": 78}
... ]
... }
...);
{ "acknowledged" : true, "insertedId" : 102 }在find()方法的帮助下显示集合中的所有文档-
> db.demo245.find();
这将产生以下输出-
{
"_id" : 101, "deatils" : [
{ "DueDate" : ISODate("2019-01-10T00:00:00Z"), "Value" : 45 },
{ "DueDate" : ISODate("2019-11-10T00:00:00Z"), "Value" : 34 }
]
}
{
"_id" : 102, "details" : [
{ "DueDate" : ISODate("2019-12-11T00:00:00Z"), "Value" : 29 },
{ "DueDate" : ISODate("2019-03-10T00:00:00Z"), "Value" : 78 } \
]
}以下是按子文档排序的查询-
> db.demo245.aggregate([
... { "$unwind": "$details" },
... { "$sort": { "_id": 1, "details.Value": -1 } },
... { "$group": {
... "_id": "$_id",
... "details": { "$push": "$details" }
... }},
... { "$sort": { "details.Value": -1 } }
...])这将产生以下输出-
{ "_id" : 102, "details" : [ { "DueDate" : ISODate("2019-03-10T00:00:00Z"), "Value" : 78 }, { "DueDate" : ISODate("2019-12-11T00:00:00Z"), "Value" : 29 } ] }