MongoDB基础知识

一.文档

文档是MongoDB的核心概念。文档就是键值对的一个有序集。注意：键是唯一的

如下：

{
    "title":"test1",
    "content":"There is study",
    "date": new Date()
    }

　　

二.集合

一组文档，相当与一张表，是动态模式

三.数据库

多个集合可以组成数据库

四.MongoDB shell简介

MongoDB 自带JavaScript shell，可在shell中使用命令行与MongoDB实例交互

shell中的基本操作

a.创建

insert

> post = {

...     "title":"test1",

...     "content":"There is study",

...     "date": new Date()

...     }

{

"title" : "test1",

"content" : "There is study",

"date" : ISODate("2020-07-28T05:49:53.951Z")

}

> db.blog.insert(post)

WriteResult({ "nInserted" : 1 })

b.读取

find

> db.blog.find()

{ "_id" : ObjectId("5f1f8fc39da18cf3e2cf8071"), "title" : "test1", "content" : "There is study", "date" : ISODate("2020-07-28T02:38:59.968Z"), "width" : 3 }

{ "_id" : ObjectId("5f1fb9909da18cf3e2cf8072"), "title" : "test2", "content" : "There is study", "date" : ISODate("2020-07-28T05:37:20.426Z") }

{ "_id" : ObjectId("5f1fba699da18cf3e2cf8073"), "title" : "test3", "content" : "There is study", "date" : ISODate("2020-07-28T05:40:57.366Z"), "study" : [ "english", "chinese" ] }

{ "_id" : ObjectId("5f1fbaf49da18cf3e2cf8074"), "title" : "test4", "content" : "There is study", "date" : ISODate("2020-07-28T05:43:16.673Z"), "study" : [ "english", "chinese" ], "lickly" : { "food" : "mifan", "ball" : "football" } }

{ "_id" : ObjectId("5f1fbca0837f599809534b75"), "title" : "test1", "content" : "There is study", "date" : ISODate("2020-07-28T05:49:53.951Z") }

findOne

> db.blog.findOne()

{

"_id" : ObjectId("5f1f8fc39da18cf3e2cf8071"),

"title" : "test1",

"content" : "There is study",

"date" : ISODate("2020-07-28T02:38:59.968Z"),

"width" : 3

}

c.更新

update,至少有两个参数：第一个是限定条件（用于匹配待更新的文档），第二个是新的文档

> post.conments = []

[ ]

> db.blog.update({"title":"test1"},post)

WriteResult({ "nMatched" : 1, "nUpserted" : 0, "nModified" : 1 })

> db.blog.find({"title":"test1"})

{ "_id" : ObjectId("5f1f8fc39da18cf3e2cf8071"), "title" : "test1", "content" : "There is study", "date" : ISODate("2020-07-28T05:49:53.951Z"), "conments" : [ ] }

d.删除

remove

> db.blog.remove({"title":"test1"})

五.数据类型

1.基本数据类型

.null

null用于表示空值或者不存在的字段

"conmments" : null

.布尔型

ture、false

.数值

"width" : 12.4
height:NumberInt(3)

.字符串

"title" : "test1"

.日期

"date" : new Date()

.正则表达式

{"title":/test/}

.数组

    "study" : [ 
        "english", 
        "chinese"
    ]

.内嵌文档

    "lickly" : {
        "food" : "mifan",
        "ball" : "football"
    }

.对象id

"_id" : ObjectId("5f1fb9909da18cf3e2cf8072")