MongoDB笔记

数据库的安装

自行下载安装包并安装

数据库的运行和连接,以及以下简单的使用

一些简单的操作

# 连接mongodb数据库
mongo (database_name) # 如果不输入数据库名会默认连接到mongodb自带的一个数据库test，如果指定了数据库名就会连接到该数据库

#切换数据库
use database_name;

#查看所有的数据库
show databases;

#查看所有的collection
show collections;

使用python代码中连接到数据库

import pymongo

connection = pymongo.MongoClient('localhost', 27017)

db = connection.test  # db指向test数据库
collection = db.mycollection

items = collection.find()
print(items['key'])

C++ 访问mongodb

安装参考[1]。

CRUD操作

id的构成 12 bytes hex

4+3+2+3
timestamp + mac address + pid + counter
timestamp是unix timestamp，mac address 是 mongd运行的网卡mac address，pid是process id，

create document

create one document(insertOne)

1	db.collection_one.insertOne({"key_one":"value","key_two":"value"})

create many documents（有order,insertMany）

db.collection_one.insertMany(
[
{"key_one":"value","key_two":"value"},
{"key_one":"value","key_two":"value"},
{"key_one":"value","key_two":"value"}
])

create many documents（无order,insertMany）

db.collection_one.insertMany(
db.collection_one.insertMany(
[
{"key_one":"value","key_two":"value"},
{"key_one":"value","key_two":"value"},
{"key_one":"value","key_two":"value"}
] , {"ordered":false})

upsert

第一个参数是一个filter选择合适的 document，第二个参数是一个更新操作for the documents were selected，第三个参数是 that if there is no matching result,if the value of upsert is true,then insert a new document,else do nothing.

1 2	db.collection_one.insertMany( db.movieDetails.updateOne({ name:"mxxhcm"}, { \$set:{lover:"mahuihui"} } , {upsert : true})

有无order的区别

有order的话遇到inset错误就会停下来，没有order的话在插入document的时候，遇到错误会跳过该条语句执行下一条语句。

read documents(query documents)

link:
https://docs.mongodb.com/manual/reference/operator/query/

查找document

查找collection_one这个collection中所有的document

1	db.collection_one.find()

查找collection_one这个collection中满足{}中条件的collection，{}中的条件需要满足anded

1	db.collection_one.find({})

pretty()表示以规范的格式展现出来查询结果

1	db.collection_one.find().pretty()

findOne表示只展示出第一条结果

1	db.collection_one.findOne()

满足{}中条件的第一条结果

1	db.collection_one.findOne({})

对document进行计数

1	db.collection_one.count()

设置查找的条件(equality match)

a.scalar equality match

1	db.collection_one.find({"key":"value","key","value"})

b.nested documents equality match

1	db.collection_one.find({"key.key2.key3":"value"})

c.equality matches on arrays

entire array value match

1	db.collection_one.find({key:[value1,value2]})

any array element fileds match a specfic value

1	db.collection_one.find({key:"value2"})

a specfiec element fields match a specfic value

1	db.collection_one.find({key.0:"value1"})

（4）cursor

（5）projection

by default,mongodb return all fields in all matching documents for query.
Projection are supplied as the second argument
db.collection_one.find({“key1”:“value”,“key2”,“value”},{“key1”:1,“key2”:1,“key3”:0,“key4”:0}).pretty()

（6）comparison operation

$eq
$gt
$gte
$lt
$lte
$ne
$in
$nin

a.在某个范围内

1	db.movieDetails.find({ runtime : { \$gt: 70, \$lte:100 } }).pretty()

b.不等于($ne)

1	db.movieDetails.find({ rated : { \$ne:"unrated" } }).pretty()

c.在($in)

1	db.movieDetails.find({rated : { \$in : ["G","PG","PG-13"] } }).pretty()

（7）element operator

a.存在某个filed($exists)

1	db.movieDetail.find( { filed_name : { \$exists: true\|false } } ).pretty()

b.某个字段的类型($type)

1	db.movieDetail.find( { filed_name : { \$type :"string"} }).pretty()

（8）logical operator

$or
$and
$not
$nor

a.逻辑或($or)

$or需要数组作为参数

1	db.movieDetails.find( { \$or: [ { field_one : {\$type : "string"} } , {field_two : {\$exist: "name" } } ] } ).pretty()

b.逻辑与($and)

$and操作支持我们在同一个filed指定多个约束条件

1	db.movieDetails.find({ \$and: [ {field_one: {\$ne :null} } , { field_one: {\$gt:60, \$lte: 100} } ] }).pretty()

（9）regex operator

1	db.movieDetails.find({ "awards.text": { \$regex: /^Won\s/} }).pretty()

（10）array operator

$all
$size
$elementMatch

a.all

1 2	db.movieDetails.find({genres : {\$all :["comedy","crime","drama"]} }).pretty() db.movieDetails.find({genres : ["comedy","crime","drama"] }).pretty()

上面两个式子是有区别的，第一个式子会匹配genres中包含"comedy",“crime”,“drama"的document
而第二个只会匹配genres为"comedy”,“crime”,"drama"的document。

b.size

1	db.movieDetails.find({country : {\$size : 3} }).pretty()

c.elementMatch

1	db.movieDetails.find({ boxOffice: { country: "UK", revenue: { \$gt: 15 } } })

9.update documents

link:
https://docs.mongodb.com/manual/reference/operator/update/

（0）some update operator

1	db.movieDetails.updateOne( { name : "mxxhcm" } , { \$inc : { age: 1} })

（1）updateOne

a.update for scalar fields

$set

1	db.movieDetails.updateOne( { name : "mxxhcm" } , { \$set : { age: 19} })

$unset

1	db.movieDetails.updateOne( { name : "mxxhcm" } , { \$unset : { age: 19} })

$inc
age后是在原来的age上加的数值

1	db.movieDetails.updateOne( { name : "mxxhcm" } , { \$set : { age: 19} })

updateOne has two arguments, the first one is a selector,the second argument is how we want to update the document.

b.update for array fields

$push

db.movieDetails.updateOne({name:"mxxhcm"} , {\$push: { reviews: { key1:value,key2:value...}  }  } )
db.movieDetails.updateOne({name:"mxxhcm"} , {\$push: { reviews:
                                                                                                { \$each: [{ key1:value,key2:value...} ,                                                                                                                        {key1:value,key2:value...} ]  }  
                                                                                              }   } )
db.movieDetails.updateOne({name:"mxxhcm"} , {\$push: { reviews:
                                                                                                { \$each: [{ key1:value,key2:value...} ,                                                                                                                        {key1:value,key2:value...} ] ,                                                                                                             \$slice:3 }  
                                                                                              }   } )
db.movieDetails.updateOne({name:"mxxhcm"} , {\$push: { reviews:
                                                                                                { \$each: [{ key1:value,key2:value...} ,                                                                                                                        {key1:value,key2:value...} ] ,                                                                                                             \$position:0,  
                                                                                                  \$slice:3 }  
                                                                                              }   } )

（2）updateMany

the same as updateOne

（3）replaceOne

1	db.movieDetail.replcaeOne({},{})

the first argument is a filter,the second argument is the thing that replace what the filter choose,it can be a document,or a variable point to a document.

10. using mongdb by pymongo

见代码

（1）sort，skip，limit

sort > skip > limit

cursor.sort('student_id',pymongo.ASCENDING).skip(4).limit(3)
in python file:
cursor.sort(  [ ('student_id',pymongo.ASCENDING) , ('score',pymongo.DESCENDING) ] ).skip(4).limit(3)
in mongo shell:
cursor.sort(  [ {'student_id':1}, {'score',-1)} ] ).skip(4).limit(3)

####（2）find,find_one,cursors
####（3）project
####（4）regex
####（5）insert
####（6）update
####（7）
There is a intervening between find and update,so maybe you find and update is not the same one.

参考文献

1.http://mongocxx.org/mongocxx-v3/installation/