Python Data Access 简明教程

Python MongoDB - Query

在使用 find() 方法检索时，您可以使用查询对象过滤文档。您可以将指定所需文档条件的查询作为参数传递给此方法。

While retrieving using find() method, you can filter the documents using the query object. You can pass the query specifying the condition for the required documents as a parameter to this method.

Operators

以下是 MongoDB 中查询中使用的运算符列表。

Following is the list of operators used in the queries in MongoDB.

Operation

Syntax

Example

Equality

{"key" : "value"}

db.mycol.find({"by":"tutorials point"})

Less Than

{"key" :{$lt:"value"}}

db.mycol.find({"likes":{$lt:50}})

Less Than Equals

{"key" :{$lte:"value"}}

db.mycol.find({"likes":{$lte:50}})

Greater Than

{"key" :{$gt:"value"}}

db.mycol.find({"likes":{$gt:50}})

Greater Than Equals

{"key" {$gte:"value"}}

db.mycol.find({"likes":{$gte:50}})

Not Equals

{"key":{$ne: "value"}}

db.mycol.find({"likes":{$ne:50}})

Example1

以下示例检索名称为 sarmista 的集合中的文档。

Following example retrieves the document in a collection whose name is sarmista.

from pymongo import MongoClient

#Creating a pymongo client
client = MongoClient('localhost', 27017)

#Getting the database instance
db = client['sdsegf']

#Creating a collection
coll = db['example']

#Inserting document into a collection
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 ......")

#Retrieving data
print("Documents in the collection: ")

for doc1 in coll.find({"name":"Sarmista"}):
   print(doc1)

Output

Data inserted ......
Documents in the collection:
{'_id': '1005', 'name': 'Sarmista', 'age': '23', 'city': 'Delhi'}

Example2

以下示例检索 age 值大于 26 的集合中的文档。

Following example retrieves the document in a collection whose age value is greater than 26.

from pymongo import MongoClient

#Creating a pymongo client
client = MongoClient('localhost', 27017)

#Getting the database instance
db = client['ghhj']

#Creating a collection
coll = db['example']

#Inserting document into a collection
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 ......")

#Retrieving data
print("Documents in the collection: ")

for doc in coll.find({"age":{"$gt":"26"}}):
   print(doc)

Output

Data inserted ......
Documents in the collection:
{'_id': '1002', 'name': 'Rahim', 'age': '27', 'city': 'Bangalore'}
{'_id': '1003', 'name': 'Robert', 'age': '28', 'city': 'Mumbai'}