MongoDB基本语法

男娘i 2022-04-15 05:46 188阅读 0赞

# 数据库对比 #

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使用非授权的方式去启动MongoDB

![2018112211340334.png][]

输入mongo

## 进入mongoDB的操作终端 ##

mongo

## 查询所有的数据库 ##

show dbs

## 创建数据库,如创建一个demo库 ##

use demo

![20181122113603845.png][]

mongodb数据库创建了库show dbs还看不见，必须网里面插入数据才能看见，这个和mysql不一样

## 创建表 ##

，(实际上它是集合)，如创建一个user表

db.createCollection("user")

![20181122113814954.png][]

还有一种创建方式,通过表名或者正规点说叫做集合名点的方式去创建并插入数据

db.users.insert(\{id:123,name:'hello'\})

![20181122114039752.png][]

## 查看当前数据库的集合 ##

show collertions

我们可以发现我们查询出了两个集合，一个user集合一个users集合

![20181122114124758.png][]

## 删除数据库 ##

db.dropDatabase()

![20181122114307874.png][]

## 创建一个数据库 ##

use demo

![20181122114343185.png][]

## 插入一条数据 ##

db.user.insert(\{id:1\})

![20181122114424870.png][]

![20181122114508533.png][]

## 查询集合 ##

![20181122114525340.png][]

## 删除集合 ##

![20181122114556143.png][]

*  插入文档

## 插入一条数据 ##

db.user.insert(\{userId:101,userName:'jack,userAge:28,class:\{name:'imooc',num:10\}\})

db.user.insert(\{userId:102,userName:'tom,userAge:38,class:\{name:'baidu',num:20\}\})

db.user.insert(\{userId:103,userName:'jack001,userAge:58,class:\{name:'taobao',num:30\}\})

![20181122114832300.png][]

![20181122114934770.png][]

## 查询数据 ##

db.user.find()  表示查看所有数据

![20181122115039587.png][]

db.user.find().pretty()  查询数据并格式化 window系统不一定支持

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### 查询第一条数据 ###

db.user.findOne()

![20181122115213561.png][]

*  更新文档

## 跟新数据 ##

，将userName为jack的用户，年龄设置为30,大家要记住基于mongodb操作都必须是对象，

就是查询条件必须是Object，设置的值也必须是Object

db.user.update(\{userName:'jack'\},\{$set:\{userAge:30\}\})

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## 子文档更新 ##

查询userName，把它的子文档更新，更新子文档的key要设置为子文档名.键

![watermark_type_ZmFuZ3poZW5naGVpdGk_shadow_10_text_aHR0cHM6Ly9ibG9nLmNzZG4ubmV0L3h5cGhm_size_16_color_FFFFFF_t_70 3][]

## 查询子文档 ##

db.user.find(\{'class.name':imooc\})

db.user.find(\{'class.name':baidu\})

![20181122115952675.png][]

## 条件查询 ##

查询年龄大于20的      大于$gt

db.user.find(\{userAge:\{$gt:20\}\})

![20181122124339423.png][]

查询年龄大于40

db.user.find(\{userAge:\{$gt:40\}\})

![20181122124411340.png][]

查询年龄小于40     小于$lt

db.user.find(\{userAge:\{$lt:40\}\})

![2018112212444862.png][]

查询年龄等于58的    等于$eq

db.user.find(\{userAge:\{$eq:58\}\})

![20181122124527419.png][]

查询年龄大于等于38   大于等于$gte

db.user.find(\{userAge:\{$gte:38\}\})

![201811221246114.png][]

*  删除文档

## 删除一条数据 ##

如：删除userId=101的用户数据

db.user.remove(\{userId:101\})

![20181122124734584.png][]

*  查询文档

![20181122124800119.png][]

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