如何在 MongoDB 中执行降序排序?
mongodbdatabasebig data analytics
要执行升序排序，语法如下:
db.yourCollectionName.find().sort({yourField:1});
为了理解这个概念，我们创建一个包含文档的集合。创建包含文档的集合的查询如下:
> db.sortingDemo.insertOne({"Value":100});
{
"acknowledged" : true,
"insertedId" : ObjectId("5c8f8e2ed3c9d04998abf006")
}
> db.sortingDemo.insertOne({"Value":1});
{
"acknowledged" : true,
"insertedId" : ObjectId("5c8f8e31d3c9d04998abf007")
}
> db.sortingDemo.insertOne({"Value":150});
{
"acknowledged" : true,
"insertedId" : ObjectId("5c8f8e34d3c9d04998abf008")
}
> db.sortingDemo.insertOne({"Value":250});
{
"acknowledged" : true,
"insertedId" : ObjectId("5c8f8e37d3c9d04998abf009")
}
> db.sortingDemo.insertOne({"Value":5});
{
"acknowledged" : true,
"insertedId" : ObjectId("5c8f8e3bd3c9d04998abf00a")
}
> db.sortingDemo.insertOne({"Value":199});
{
"acknowledged" : true,
"insertedId" : ObjectId("5c8f8e3ed3c9d04998abf00b")
}
> db.sortingDemo.insertOne({"Value":243});
{
"acknowledged" : true,
"insertedId" : ObjectId("5c8f8e44d3c9d04998abf00c")
}
> db.sortingDemo.insertOne({"Value":290});
{
"acknowledged" : true,
"insertedId" : ObjectId("5c8f8e48d3c9d04998abf00d")
}
使用 find() 方法显示集合中的所有文档。查询如下 −
> db.sortingDemo.find().pretty();
以下是输出 −
{ "_id" : ObjectId("5c8f8e2ed3c9d04998abf006"), "Value" : 100 }
{ "_id" : ObjectId("5c8f8e31d3c9d04998abf007"), "Value" : 1 }
{ "_id" : ObjectId("5c8f8e34d3c9d04998abf008"), "Value" : 150 }
{ "_id" : ObjectId("5c8f8e37d3c9d04998abf009"), "Value" : 250 }
{ "_id" : ObjectId("5c8f8e3bd3c9d04998abf00a"), "Value" : 5 }
{ "_id" : ObjectId("5c8f8e3ed3c9d04998abf00b"), "Value" : 199 }
{ "_id" : ObjectId("5c8f8e44d3c9d04998abf00c"), "Value" : 243 }
{ "_id" : ObjectId("5c8f8e48d3c9d04998abf00d"), "Value" : 290 }
Here is the query to get result in descending order. The query is as follows:
> db.sortingDemo.find().sort({Value:-1});
以下是输出 −
{ "_id" : ObjectId("5c8f8e48d3c9d04998abf00d"), "Value" : 290 }
{ "_id" : ObjectId("5c8f8e37d3c9d04998abf009"), "Value" : 250 }
{ "_id" : ObjectId("5c8f8e44d3c9d04998abf00c"), "Value" : 243 }
{ "_id" : ObjectId("5c8f8e3ed3c9d04998abf00b"), "Value" : 199 }
{ "_id" : ObjectId("5c8f8e34d3c9d04998abf008"), "Value" : 150 }
{ "_id" : ObjectId("5c8f8e2ed3c9d04998abf006"), "Value" : 100 }
{ "_id" : ObjectId("5c8f8e3bd3c9d04998abf00a"), "Value" : 5 }
{ "_id" : ObjectId("5c8f8e31d3c9d04998abf007"), "Value" : 1 }
