Python MongoDB - 排序

检索集合的内容时，可以使用 sort() 方法按升序或降序对其进行排序和排列。

对于此方法，您可以传递字段和排序顺序，即 1 或 -1。其中，1 表示升序，-1 表示降序。

语法

以下是 sort() 方法的语法。

>db.COLLECTION_NAME.find().sort({KEY:1})

示例

假设我们创建了一个集合并向其中插入了 5 个文档，如下所示 −

> use testDB
switched to db testDB
> db.createCollection("myColl")
{ "ok" : 1 }
> data = [
   ... {"_id": "1001", "name": "Ram", "age": "26", "city": "Hyderabad"},
   ... {"_id": "1002", "name": "Rahim", "age": 27, "city": "Bangalore"},
   ... {"_id": "1003", "name": "Robert", "age": 28, "city": "Mumbai"},
   ... {"_id": "1004", "name": "Romeo", "age": 25, "city": "Pune"},
   ... {"_id": "1005", "name": "Sarmista", "age": 23, "city": "Delhi"},
   ... {"_id": "1006", "name": "Rasajna", "age": 26, "city": "Chennai"}
]
> db.sample.insert(data)
BulkWriteResult({
   "writeErrors" : [ ],
   "writeConcernErrors" : [ ],
   "nInserted" : 6,
   "nUpserted" : 0,
   "nMatched" : 0,
   "nModified" : 0,
   "nRemoved" : 0,
   "upserted" : [ ]
})

下一行检索集合中的所有文档，这些文档按年龄升序排列。

> db.sample.find().sort({age:1})
{ "_id" : "1005", "name" : "Sarmista", "age" : 23, "city" : "Delhi" }
{ "_id" : "1004", "name" : "Romeo", "age" : 25, "city" : "Pune" }
{ "_id" : "1006", "name" : "Rasajna", "age" : 26, "city" : "Chennai" }
{ "_id" : "1002", "name" : "Rahim", "age" : 27, "city" : "Bangalore" }
{ "_id" : "1003", "name" : "Robert", "age" : 28, "city" : "Mumbai" }
{ "_id" : "1001", "name" : "Ram", "age" : "26", "city" : "Hyderabad" }

使用 python 对文档进行排序

为了按升序或降序对查询结果进行排序，pymongo 提供了 sort() 方法。向此方法传递一个数值，表示结果中需要的文档数量。

默认情况下，此方法根据指定字段按升序对文档进行排序。如果需要按降序排序，请将 -1 与字段名称一起传递 −

coll.find().sort("age",-1)

示例

以下示例检索集合中的所有文档，这些文档按年龄值升序排列 −

from pymongo import MongoClient

#创建 pymongo 客户端
client = MongoClient('localhost', 27017)

#获取数据库实例
db = client['b_mydb']

#创建集合
coll = db['myColl']

#将文档插入集合
data = [
   {"_id": "1001", "name": "Ram", "age": "26", "city": "Hyderabad"},
   {"_id": "1002", "name": "Rahim", "age": "27", "city": "Bangalore"},
   {"_id": "1003", "name": "Robert", "age": "28", "city": "Mumbai"},
   {"_id": "1004", "name": "Romeo", "age": 25, "city": "Pune"},
   {"_id": "1005", "name": "Sarmista", "age": 23, "city": "Delhi"},
   {"_id": "1006", "name": "Rasajna", "age": 26, "city": "Chennai"}
]
res = coll.insert_many(data)
print("Data inserted ......")

#使用 find() 和 limit() 方法检索前 3 个文档
print("List of documents (sorted in ascending order based on age): ")

for doc1 in coll.find().sort("age"):
   print(doc1)

输出

Data inserted ......
List of documents (sorted in ascending order based on age):
{'_id': '1005', 'name': 'Sarmista', 'age': 23, 'city': 'Delhi'}
{'_id': '1004', 'name': 'Romeo', 'age': 25, 'city': 'Pune'}
{'_id': '1006', 'name': 'Rasajna', 'age': 26, 'city': 'Chennai'}
{'_id': '1001', 'name': 'Ram', 'age': '26', 'city': 'Hyderabad'}
{'_id': '1002', 'name': 'Rahim', 'age': '27', 'city': 'Bangalore'}
{'_id': '1003', 'name': 'Robert', 'age': '28', 'city': 'Mumbai'}