Based on the use of learning [database] mongodb interfaces with python

mongodb: key-value pair form, suitable for reptiles, Baidu maps; document - similar to the dictionary, composed by the document collection.
distributed:

reliability
Scalability
Resource Sharing
Faster

command

Enter: mongo

 ~$ mongo
 MongoDB shell version v3.6.3
 ……
 2020-02-22T16:04:39.509+0800 ICONTROL  [initandlisten]

Library operations

Show all databases: show dbs

 > show dbs
 admin     0.000GB
 config    0.000GB
 local     0.000GB

Use database: use databases, there is used, if any, to create, if not a collection of the database, the database does not display the dbs
```
 > use python
 switched to db python
```
View current database: db
```
 > db
 python
```
Delete the current database: db.dropDatabase () is case-sensitive, hump logo

Set operations

Create Collection: db.createCollection ( 'name')
```
 > db.createCollection('stu')
 { "ok" : 1 }
```
Displays the current database of all collections: show collections
```
 > show collections
 stu
```
To delete a collection:. Db collection name .drop ()

Document Actions

increase

Inserted into the collection document:. Db name set .insert ({ 'key': value, 'key': value}) _id unique identification is automatically added, may be added manually { '_id': 123}
```
 > db.stu.insert({'_id':123,'name':'zhen','age':21})
 WriteResult({ "nInserted" : 1 })
```

Inserting rows of data:. Db name set .insert ([{}, {}, {}])

> db.stu.insert([{'name':'lili','age':11},{'name':'ilil','age':21}])
BulkWriteResult({
	"writeErrors" : [ ],
	"writeConcernErrors" : [ ],
	"nInserted" : 2,
	"nUpserted" : 0,
	"nMatched" : 0,
	"nModified" : 0,
	"nRemoved" : 0,
	"upserted" : [ ]
})

check

Query contents of the collection: db collection name .find ().

> db.stu.find()
{ "_id" : ObjectId("5e53c343717845eaf7f530cc"), "name" : "li", "age" : 22 }

Beautify display the query contents of the collection: db collection name .find () pretty ()..

> db.stu.find().pretty()
{ "_id" : ObjectId("5e53c343717845eaf7f530cc"), "name" : "li", "age" : 22 }
{ "_id" : 123, "name" : "zhen", "age" : 21 }
{
	"_id" : ObjectId("5e53c45e717845eaf7f530cd"),
	"name" : "lili",
	"age" : 11
}

Satisfy the query criteria:. Db name set .find ({ 'key': value}) key can not be quoted
```
> db.stu.find({name:'li'})
```

Operators

不等于：$ne
大于：$gt
小于：$lt
大于等于：$gte
小于等于：$lte
db.集合名字.find({key:{$gt:20}})

And $ query: db name set .find. ({$ And: [{key: value}, {}]})
$ Or query: db name set .find. ({$ Or: [{key: value}, {}]})
```
db.stu.find({$or:[{name:'li'},{age:{$gt:11}}]})
```
$or 里嵌套and 查询：db.集合名字.find({ $KaTeX parse error: Expected '}', got 'EOF' at end of input: or:[{$ and:[{key:value},{key:value}]},{$and:[{key:value},{key:value}]}]})

change

Modify: db name .Update set (condition modified {}, {} modified value), only a plurality of the condition of a modification; belongs to cover all modifications, add the parameter $ set to cover only the non-modified
```
覆盖：db.stu.update({age:22},{name:'xxx'})
修改：db.stu.update({age:22},{$set:{name:'xxx'}})
全部修改：db.stu.update({age:22},{$set:{name:'xxx'}},{multi:true})
```

delete

Delete the document: db collection .remove ({key: value}). Do not give conditions, only {} will delete all, delete only the first parameter qualifying: justOne: true
```
只删除一条：db.stu.remove({age:22},{justOne:true})
```

pycharm operation mongo

Import library
```
 import pymongo
```
Establish a connection --pymongo.MongoClient ()
```
 clinent = pymongo.MongoClient()
```
Connect to the database --clinent [ 'python37']
```
 clinent['python37']
```
Connection sets --db [ 'student']
```
 my_collection = db['student']
```

Set operations - CRUD

 增一条——insert_one()
 my_collection.insert_one({'name':'li','age':13,'sex':'f'})
 增多条——insert_many()
 my_collection.insert_many([
  {},
  {},
  {}
       ])
 查询——find_one()
 res = my_collection.find_one() # 查询一条
 res = my_collection.find()  #查询全部，返回的是可迭代的结果，也可以list(res)强转为列表
 修改——update_one()

 my_collection.update_one({'name':'value'},	{'$set':{'age':20}})  参数要用字符串的形式传递
 删除——delete_one()  注意不是remove
 res = my_collection.delete_one({'name':'value'})

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