MongoDB 4.X基础教程
mongodb
一、MongoDB介绍
MongoDB是一个基于分布式文件存储的数据库。
由C++语言编写。旨在为WEB应用提供可扩展的 高性能数据存储解决方案。
MongoDB是一个介于关系型数据库和非关系数据库之间的产品，是非关系数据库当中功能最丰富，最像关系数据库的。
MongoDB支持的数据结构非常松散，是类似JSON的BJSON格式，因此可以存储比较复 杂的数据类型。Mongo最大的特点是它支持的查询语言非常强大，其语法有点类似于面向对象的查询语 言，几乎可以实现类似关系数据库单表查询的绝大部分功能，而且还支持对数据建立索引。
MongoDB数据操作基于json格式
<span style="font-size: 16px;"> { "userName":"admin", "password":123456 }<br/></span>登录后复制
二、MongoDB安装
1.MongoDB下载
网址：https://www.mongodb.com/try/download/community
上图在选择版本的时候根据自己系统选择，有Windowns、LInux、CentOS、Ubuntu等可供 选择。
2.MongoDB安装
下载的 .msi 文件，下载后双击该文件，按操作提示安装即可。
安装过程中，你可以通过点击 "Custom(自定义)" 按钮来设置你的安装目录，建议不要安装在C 盘。
全程点击next安装，但是这一步需要注意，这里是安装可视化组件，默认是选择状态，这里需 要取消选中，否则在安装的过程中要下载可视化组件，比较慢，甚至有时候会报错：
3.MongoDB环境变量配置
在桌面右键 此电脑>>>属性>>>高级系统设置>>>高级>>>环境变量>>>找到path>>>选择编辑 >>>新建
在打开的环境变量中MongoDB安装的bin路径复制到新建目录中
然后点击所有的确定即可完成环境变量配置
4.验证安装是否成功
打开CMD命令窗口，输入mongo，出现以下提示信息，说明安装成功。
<span style="font-size: 16px;">C:\Users\***.DESKTOP-C1RC9P2>mongo<br/>MongoDB shell version v4.4.2-rc0<br/>connecting to: mongodb://127.0.0.1:27017/?compressors=disabled&gssapiServiceName=mongodb<br/>Implicit session: session { "id" : UUID("df31999e-cb62-4f71-8a18-7db8723c514f") }<br/>MongoDB server version: 4.4.2-rc0<br/>---<br/>The server generated these startup warnings when booting:<br/> 2020-10-30T16:25:16.503+08:00: Access control is not enabled for the database. Read and write access to data and configuration is unrestricted<br/>---<br/>---<br/> Enable MongoDB's free cloud-based monitoring service, which will then receive and display<br/> metrics about your deployment (disk utilization, CPU, operation statistics, etc).<br/><br/> The monitoring data will be available on a MongoDB website with a unique URL accessible to you<br/> and anyone you share the URL with. MongoDB may use this information to make product<br/> improvements and to suggest MongoDB products and deployment options to you.<br/><br/> To enable free monitoring, run the following command: db.enableFreeMonitoring()<br/> To permanently disable this reminder, run the following command: db.disableFreeMonitoring()<br/></span>登录后复制
三、MongoDB使用基本介绍
MongoDB属于非关系型数据库，其数据库、表、字段等和关系型数据库 （如：MySQL数据库）有一定的差别；
MongoDB中的集合就相当于关系型数据库中的表 MongoDB中的json字符串的键相当于关系型数据库中的列名；
在操作MongoDB数据的时候全部使用json数据格式。
1.查看数据库名
查看所有数据库名
<span style="font-size: 16px;">命令：<br/> show dbs<br/></span>
登录后复制
<span style="font-size: 16px;"> > show dbs<br/> admin 0.000GB<br/> config 0.000GB<br/> local 0.000GB<br/></span>
登录后复制
这三个数据库是默认系统数据库，不能删除。
2. 查看集合
查看集合前提是要先指定使用哪一个数据库
<span style="font-size: 16px;">命令：<br/>ues 数据库名 show collections<br/></span>
登录后复制
<span style="font-size: 16px;">> use admin <br/>switched to db admin <br/>> show collections <br/>system.version<br/></span>
登录后复制
system.version 就是admin这个数据库中的表
3.查询集合中的数据
这里先简单介绍查询集合中的所有数据，方便后面学习。
查询集合中的所有数据，这里查询的是系统数据库admin中的 system.version 集合
<span style="font-size: 16px;">命令：<br/> db.集合名.find()<br/></span>
登录后复制
<span style="font-size: 16px;">> db.system.version.find()<br/>{ "_id" : "featureCompatibilityVersion", "version" : "4.4" }<br/></span>登录后复制
这里的_id是集合的键，每个集合里面默认存在，version是集合中的另一个键，相当于关系型 数据库中的字段
四、创建数据库及添加数据
MongoDB不能够直接创建数据库，需要添加一条数据才能创建
1.创建数据库和插入数据
先指定创建的数据
然后执行添加数据命令
<span style="font-size: 16px;">> use company<br/>switched to db company<br/>> db.emp.insert({"empno":100,"ename":"admin","sex":"男","age":20,"salary":800.00,"deptno":10})<br/>WriteResult({ "nInserted" : 1 })<br/></span>登录后复制
这里插入了6列数据，分别是员工的编号，姓名，性别，年龄，薪资及所在的部门
<span style="font-size: 16px;">WriteResult({ "nInserted" : 1 })<br/></span>登录后复制
表示一行数据插入成功,说明创建数据成功，同时添加 了一套数据,我们可以继续添加
<span style="font-size: 16px;">> db.emp.insert({"empno":101,"ename":"张三","sex":"女","age":30,"salary":2500.00,"deptno":20})})})})<br/>WriteResult({ "nInserted" : 1 })</span>登录后复制
随着数据的插入，数据库也随着创建成功。
五、查询数据
查询所有数据，在查询数据前要先指定使用哪个数据库，再查询数据库中的所有集合，根据相应集 合再查询数据。
1.查询所有数据
<span style="font-size: 16px;">命令：<br/>db.集合名.find() </span>
登录后复制
<span style="font-size: 16px;">指定对哪个数据库操作<br/> > use company<br/> switched to db company<br/>查询指定数据库后里面的所有集合<br/> > show collections<br/>emp<br/>查询所有数据，一共12条数据：<br/> > db.emp.find()<br/><br/>{ "_id" : ObjectId("5f9c1c5b5df291fa8194b91b"), "empno" : 100, "ename" : "admin", "sex" : "男", "age" : 20, "salary" : 800, "deptno" : 10 }<br/>{ "_id" : ObjectId("5f9c1dfc5df291fa8194b91c"), "empno" : 101, "ename" : "张三", "sex" : "女", "age" : 30, "salary" : 2500, "deptno" : 20 }<br/>{ "_id" : ObjectId("5f9c20945df291fa8194b91d"), "empno" : 102, "ename" : "张良", "sex" : "男", "age" : 25, "salary" : 3000, "deptno" : 20 }<br/>{ "_id" : ObjectId("5f9c21055df291fa8194b91e"), "empno" : 103, "ename" : "李明", "sex" : "女", "age" : 30, "salary" : 1800, "deptno" : 30 }<br/>{ "_id" : ObjectId("5f9c215f5df291fa8194b91f"), "empno" : 104, "ename" : "李菲菲", "sex" : "女", "age" : 28, "salary" : 4200, "deptno" : 20 }<br/>{ "_id" : ObjectId("5f9c219b5df291fa8194b921"), "empno" : 106, "ename" : "李四", "sex" : "男", "age" : 34, "salary" : 12000, "deptno" : 10 }<br/>{ "_id" : ObjectId("5f9c21a75df291fa8194b922"), "empno" : 106, "ename" : "李四", "sex" : "男", "age" : 34, "salary" : 12000, "deptno" : 10 }<br/>{ "_id" : ObjectId("5f9c21d85df291fa8194b923"), "empno" : 107, "ename" : "王三", "sex" : "女", "age" : 27, "salary" : 5000, "deptno" : 20 }<br/>{ "_id" : ObjectId("5f9c22185df291fa8194b924"), "empno" : 108, "ename" : "李元芳", "sex" : "男", "age" : 33, "salary" : 10000, "deptno" : 30 }<br/>{ "_id" : ObjectId("5f9c227d5df291fa8194b926"), "empno" : 110, "ename" : "刘静", "sex" : "女", "age" : 25, "salary" : 3500, "deptno" : 10 }<br/>{ "_id" : ObjectId("5f9c371b5df291fa8194b927"), "empno" : 105, "ename" : "张四", "sex" : "男", "age" : 32, "salary" : 8000, "deptno" : 30 }<br/>{ "_id" : ObjectId("5f9c376a29491ade8d9d3e79"), "empno" : 109, "ename" : "李元静", "sex" : "女", "age" : 32, "salary" : 1600, "deptno" : 30 }<br/></span>登录后复制
2.去掉集合中重复的数据
<span style="font-size: 16px;">命令：<br/>> db.集合名.distinct("ename")<br/></span>登录后复制
<span style="font-size: 16px;">> db.emp.distinct("ename")<br/><br/>[<br/> "admin",<br/> "刘静",<br/> "张三",<br/> "张四",<br/> "张良",<br/> "李元芳",<br/> "李元静",<br/> "李四",<br/> "李明",<br/> "李菲菲",<br/> "王三"<br/>]<br/></span>登录后复制
上面的结果“李四”重复被去掉了
3. 查询年龄等于25的数据
这里的“age”可以不加“ ”，直接写成{age:25}
<span style="font-size: 16px;">> db.emp.find({"age":25})<br/><br/>{ "_id" : ObjectId("5f9c20945df291fa8194b91d"), "empno" : 102, "ename" : "张良", "sex" : "男", "age" : 25, "salary" : 3000, "deptno" : 20 }<br/>{ "_id" : ObjectId("5f9c227d5df291fa8194b926"), "empno" : 110, "ename" : "刘静", "sex" : "女", "age" : 25, "salary" : 3500, "deptno" : 10 }<br/></span>登录后复制
4. 查询ename=“李元芳“的数据
<span style="font-size: 16px;">> db.emp.find({"ename":"李元芳"})<br/><br/>{ "_id" : ObjectId("5f9c22185df291fa8194b924"), "empno" : 108, "ename" : "李元芳", "sex" : "男", "age" : 35, "salary" : 8000, "deptno" : 30 }<br/></span>登录后复制
5. 查询age>30岁的员工数据
<span style="font-size: 16px;">> db.emp.find({"age":{$gt:30}})<br/><br/>{ "_id" : ObjectId("5f9c21855df291fa8194b920"), "empno" : 105, "ename" : "张四", "sex" : "男", "age" : 32, "salary" : 8000, "deptno" : 30 }<br/>{ "_id" : ObjectId("5f9c219b5df291fa8194b921"), "empno" : 106, "ename" : "李四", "sex" : "男", "age" : 35, "salary" : 12000, "deptno" : 10 }<br/>{ "_id" : ObjectId("5f9c21a75df291fa8194b922"), "empno" : 106, "ename" : "李四", "sex" : "男", "age" : 35, "salary" : 12000, "deptno" : 10 }<br/>{ "_id" : ObjectId("5f9c22185df291fa8194b924"), "empno" : 108, "ename" : "李元芳", "sex" : "男", "age" : 35, "salary" : 8000, "deptno" : 30 }<br/>{ "_id" : ObjectId("5f9c22445df291fa8194b925"), "empno" : 109, "ename" : "李元静", "sex" : "女", "age" : 35, "salary" : 15000, "deptno" : 36 }<br/></span>登录后复制
6. 查询age<25的员工数据
<span style="font-size: 16px;">> db.emp.find({"age":{$lt:25}})<br/><br/>{ "_id" : ObjectId("5f9c1c5b5df291fa8194b91b"), "empno" : 100, "ename" : "admin", "sex" : "男", "age" : 20, "salary" : 800, "deptno" : 10 }<br/></span>登录后复制
7.查询age>=30的员工数据
<span style="font-size: 16px;">> db.emp.find({"age":{$gte:30}})<br/><br/>{ "_id" : ObjectId("5f9c1dfc5df291fa8194b91c"), "empno" : 101, "ename" : "张三", "sex" : "女", "age" : 30, "salary" : 2500, "deptno" : 20 }<br/>{ "_id" : ObjectId("5f9c21055df291fa8194b91e"), "empno" : 103, "ename" : "李明", "sex" : "女", "age" : 30, "salary" : 1800, "deptno" : 30 }<br/>{ "_id" : ObjectId("5f9c21855df291fa8194b920"), "empno" : 105, "ename" : "张四", "sex" : "男", "age" : 32, "salary" : 8000, "deptno" : 30 }<br/>{ "_id" : ObjectId("5f9c219b5df291fa8194b921"), "empno" : 106, "ename" : "李四", "sex" : "男", "age" : 35, "salary" : 12000, "deptno" : 10 }<br/>{ "_id" : ObjectId("5f9c21a75df291fa8194b922"), "empno" : 106, "ename" : "李四", "sex" : "男", "age" : 35, "salary" : 12000, "deptno" : 10 }<br/>{ "_id" : ObjectId("5f9c22185df291fa8194b924"), "empno" : 108, "ename" : "李元芳", "sex" : "男", "age" : 35, "salary" : 8000, "deptno" : 30 }<br/>{ "_id" : ObjectId("5f9c22445df291fa8194b925"), "empno" : 109, "ename" : "李元静", "sex" : "女", "age" : 35, "salary" : 15000, "deptno" : 36 }<br/></span>登录后复制
8. 查询age<=30的员工数据
<span style="font-size: 16px;">> db.emp.find({"age":{$lte:30}})<br/><br/>{ "_id" : ObjectId("5f9c1c5b5df291fa8194b91b"), "empno" : 100, "ename" : "admin", "sex" : "男", "age" : 20, "salary" : 800, "deptno" : 10 }<br/>{ "_id" : ObjectId("5f9c1dfc5df291fa8194b91c"), "empno" : 101, "ename" : "张三", "sex" : "女", "age" : 30, "salary" : 2500, "deptno" : 20 }<br/>{ "_id" : ObjectId("5f9c20945df291fa8194b91d"), "empno" : 102, "ename" : "张良", "sex" : "男", "age" : 25, "salary" : 3000, "deptno" : 20 }<br/>{ "_id" : ObjectId("5f9c21055df291fa8194b91e"), "empno" : 103, "ename" : "李明", "sex" : "女", "age" : 30, "salary" : 1800, "deptno" : 30 }<br/>{ "_id" : ObjectId("5f9c215f5df291fa8194b91f"), "empno" : 104, "ename" : "李菲菲", "sex" : "女", "age" : 28, "salary" : 4200, "deptno" : 20 }<br/>{ "_id" : ObjectId("5f9c21d85df291fa8194b923"), "empno" : 107, "ename" : "王三", "sex" : "女", "age" : 27, "salary" : 5000, "deptno" : 20 }<br/>{ "_id" : ObjectId("5f9c227d5df291fa8194b926"), "empno" : 110, "ename" : "刘静", "sex" : "女", "age" : 25, "salary" : 3500, "deptno" : 10 }<br/></span>登录后复制
9. 查询age>=25并且age<=30的员工数据
<span style="font-size: 16px;">> db.emp.find({"age":{$gte:25,$lte:30}})<br/><br/>{ "_id" : ObjectId("5f9c1dfc5df291fa8194b91c"), "empno" : 101, "ename" : "张三", "sex" : "女", "age" : 30, "salary" : 2500, "deptno" : 20 }<br/>{ "_id" : ObjectId("5f9c20945df291fa8194b91d"), "empno" : 102, "ename" : "张良", "sex" : "男", "age" : 25, "salary" : 3000, "deptno" : 20 }<br/>{ "_id" : ObjectId("5f9c21055df291fa8194b91e"), "empno" : 103, "ename" : "李明", "sex" : "女", "age" : 30, "salary" : 1800, "deptno" : 30 }<br/>{ "_id" : ObjectId("5f9c215f5df291fa8194b91f"), "empno" : 104, "ename" : "李菲菲", "sex" : "女", "age" : 28, "salary" : 4200, "deptno" : 20 }<br/>{ "_id" : ObjectId("5f9c21d85df291fa8194b923"), "empno" : 107, "ename" : "王三", "sex" : "女", "age" : 27, "salary" : 5000, "deptno" : 20 }<br/>{ "_id" : ObjectId("5f9c227d5df291fa8194b926"), "empno" : 110, "ename" : "刘静", "sex" : "女", "age" : 25, "salary" : 3500, "deptno" : 10 }<br/></span>登录后复制
10. 查询全部姓李的员工数据（模糊查询）
模糊查询一般用于查询数据量比较小的集合数据
<span style="font-size: 16px;">> db.emp.find({"ename":/李/})<br/><br/>{ "_id" : ObjectId("5f9c21055df291fa8194b91e"), "empno" : 103, "ename" : "李明", "sex" : "女", "age" : 30, "salary" : 1800, "deptno" : 30 }<br/>{ "_id" : ObjectId("5f9c215f5df291fa8194b91f"), "empno" : 104, "ename" : "李菲菲", "sex" : "女", "age" : 28, "salary" : 4200, "deptno" : 20 }<br/>{ "_id" : ObjectId("5f9c219b5df291fa8194b921"), "empno" : 106, "ename" : "李四", "sex" : "男", "age" : 35, "salary" : 12000, "deptno" : 10 }<br/>{ "_id" : ObjectId("5f9c21a75df291fa8194b922"), "empno" : 106, "ename" : "李四", "sex" : "男", "age" : 35, "salary" : 12000, "deptno" : 10 }<br/>{ "_id" : ObjectId("5f9c22185df291fa8194b924"), "empno" : 108, "ename" : "李元芳", "sex" : "男", "age" : 35, "salary" : 8000, "deptno" : 30 }<br/>{ "_id" : ObjectId("5f9c22445df291fa8194b925"), "empno" : 109, "ename" : "李元静", "sex" : "女", "age" : 35, "salary" : 15000, "deptno" : 36 }<br/></span>登录后复制
11. 查询姓名以“张”开头的员工数据
<span style="font-size: 16px;">> db.emp.find({"ename":/^张/})<br/><br/>{ "_id" : ObjectId("5f9c1dfc5df291fa8194b91c"), "empno" : 101, "ename" : "张三", "sex" : "女", "age" : 30, "salary" : 2500, "deptno" : 20 }<br/>{ "_id" : ObjectId("5f9c20945df291fa8194b91d"), "empno" : 102, "ename" : "张良", "sex" : "男", "age" : 25, "salary" : 3000, "deptno" : 20 }<br/>{ "_id" : ObjectId("5f9c21855df291fa8194b920"), "empno" : 105, "ename" : "张四", "sex" : "男", "age" : 32, "salary" : 8000, "deptno" : 30 }<br/></span>登录后复制
12. 查询以姓名以“静”结尾的员工数据
<span style="font-size: 16px;">> db.emp.find({"ename":/静$/})<br/><br/>{ "_id" : ObjectId("5f9c22445df291fa8194b925"), "empno" : 109, "ename" : "李元静", "sex" : "女", "age" : 35, "salary" : 15000, "deptno" : 36 }<br/>{ "_id" : ObjectId("5f9c227d5df291fa8194b926"), "empno" : 110, "ename" : "刘静", "sex" : "女", "age" : 25, "salary" : 3500, "deptno" : 10 }<br/></span>登录后复制
13. 查询指定列的员工数据
查询所有员工年龄的数据
<span style="font-size: 16px;">> db.emp.find({},{"age":1})<br/><br/>{ "_id" : ObjectId("5f9c1c5b5df291fa8194b91b"), "age" : 20 }<br/>{ "_id" : ObjectId("5f9c1dfc5df291fa8194b91c"), "age" : 30 }<br/>{ "_id" : ObjectId("5f9c20945df291fa8194b91d"), "age" : 25 }<br/>{ "_id" : ObjectId("5f9c21055df291fa8194b91e"), "age" : 30 }<br/>{ "_id" : ObjectId("5f9c215f5df291fa8194b91f"), "age" : 28 }<br/>{ "_id" : ObjectId("5f9c21855df291fa8194b920"), "age" : 32 }<br/>{ "_id" : ObjectId("5f9c219b5df291fa8194b921"), "age" : 35 }<br/>{ "_id" : ObjectId("5f9c21a75df291fa8194b922"), "age" : 35 }<br/>{ "_id" : ObjectId("5f9c21d85df291fa8194b923"), "age" : 27 }<br/>{ "_id" : ObjectId("5f9c22185df291fa8194b924"), "age" : 35 }<br/>{ "_id" : ObjectId("5f9c22445df291fa8194b925"), "age" : 35 }<br/>{ "_id" : ObjectId("5f9c227d5df291fa8194b926"), "age" : 25 }<br/></span>登录后复制
查询所有员工的姓名和年龄的数据
<span style="font-size: 16px;">> db.emp.find({},{"ename":1,"age":1})<br/><br/>{ "_id" : ObjectId("5f9c1c5b5df291fa8194b91b"), "ename" : "admin", "age" : 20 }<br/>{ "_id" : ObjectId("5f9c1dfc5df291fa8194b91c"), "ename" : "张三", "age" : 30 }<br/>{ "_id" : ObjectId("5f9c20945df291fa8194b91d"), "ename" : "张良", "age" : 25 }<br/>{ "_id" : ObjectId("5f9c21055df291fa8194b91e"), "ename" : "李明", "age" : 30 }<br/>{ "_id" : ObjectId("5f9c215f5df291fa8194b91f"), "ename" : "李菲菲", "age" : 28 }<br/>{ "_id" : ObjectId("5f9c21855df291fa8194b920"), "ename" : "张四", "age" : 32 }<br/>{ "_id" : ObjectId("5f9c219b5df291fa8194b921"), "ename" : "李四", "age" : 35 }<br/>{ "_id" : ObjectId("5f9c21a75df291fa8194b922"), "ename" : "李四", "age" : 35 }<br/>{ "_id" : ObjectId("5f9c21d85df291fa8194b923"), "ename" : "王三", "age" : 27 }<br/>{ "_id" : ObjectId("5f9c22185df291fa8194b924"), "ename" : "李元芳", "age" : 35 }<br/>{ "_id" : ObjectId("5f9c22445df291fa8194b925"), "ename" : "李元静", "age" : 35 }<br/>{ "_id" : ObjectId("5f9c227d5df291fa8194b926"), "ename" : "刘静", "age" : 25 }<br/></span>登录后复制
查询age>=30的员工姓名、年龄和薪资
<span style="font-size: 16px;">> db.emp.find({"age":{$gte:30}},{"ename":1,"age":1,"salary":1})<br/><br/>{ "_id" : ObjectId("5f9c1dfc5df291fa8194b91c"), "ename" : "张三", "age" : 30, "salary" : 2500 }<br/>{ "_id" : ObjectId("5f9c21055df291fa8194b91e"), "ename" : "李明", "age" : 30, "salary" : 1800 }<br/>{ "_id" : ObjectId("5f9c21855df291fa8194b920"), "ename" : "张四", "age" : 32, "salary" : 8000 }<br/>{ "_id" : ObjectId("5f9c219b5df291fa8194b921"), "ename" : "李四", "age" : 35, "salary" : 12000 }<br/>{ "_id" : ObjectId("5f9c21a75df291fa8194b922"), "ename" : "李四", "age" : 35, "salary" : 12000 }<br/>{ "_id" : ObjectId("5f9c22185df291fa8194b924"), "ename" : "李元芳", "age" : 35, "salary" : 8000 }<br/>{ "_id" : ObjectId("5f9c22445df291fa8194b925"), "ename" : "李元静", "age" : 35, "salary" : 15000 }<br/></span>登录后复制
14. 排序
按照年龄升序排列
<span style="font-size: 16px;">> db.emp.find().sort({"age":1})<br/><br/>{ "_id" : ObjectId("5f9c1c5b5df291fa8194b91b"), "empno" : 100, "ename" : "admin", "sex" : "男", "age" : 20, "salary" : 800, "deptno" : 10 }<br/>{ "_id" : ObjectId("5f9c20945df291fa8194b91d"), "empno" : 102, "ename" : "张良", "sex" : "男", "age" : 25, "salary" : 3000, "deptno" : 20 }<br/>{ "_id" : ObjectId("5f9c227d5df291fa8194b926"), "empno" : 110, "ename" : "刘静", "sex" : "女", "age" : 25, "salary" : 3500, "deptno" : 10 }<br/>{ "_id" : ObjectId("5f9c21d85df291fa8194b923"), "empno" : 107, "ename" : "王三", "sex" : "女", "age" : 27, "salary" : 5000, "deptno" : 20 }<br/>{ "_id" : ObjectId("5f9c215f5df291fa8194b91f"), "empno" : 104, "ename" : "李菲菲", "sex" : "女", "age" : 28, "salary" : 4200, "deptno" : 20 }<br/>{ "_id" : ObjectId("5f9c1dfc5df291fa8194b91c"), "empno" : 101, "ename" : "张三", "sex" : "女", "age" : 30, "salary" : 2500, "deptno" : 20 }<br/>{ "_id" : ObjectId("5f9c21055df291fa8194b91e"), "empno" : 103, "ename" : "李明", "sex" : "女", "age" : 30, "salary" : 1800, "deptno" : 30 }<br/>{ "_id" : ObjectId("5f9c21855df291fa8194b920"), "empno" : 105, "ename" : "张四", "sex" : "男", "age" : 32, "salary" : 8000, "deptno" : 30 }<br/>{ "_id" : ObjectId("5f9c219b5df291fa8194b921"), "empno" : 106, "ename" : "李四", "sex" : "男", "age" : 35, "salary" : 12000, "deptno" : 10 }<br/>{ "_id" : ObjectId("5f9c21a75df291fa8194b922"), "empno" : 106, "ename" : "李四", "sex" : "男", "age" : 35, "salary" : 12000, "deptno" : 10 }<br/>{ "_id" : ObjectId("5f9c22185df291fa8194b924"), "empno" : 108, "ename" : "李元芳", "sex" : "男", "age" : 35, "salary" : 8000, "deptno" : 30 }<br/>{ "_id" : ObjectId("5f9c22445df291fa8194b925"), "empno" : 109, "ename" : "李元静", "sex" : "女", "age" : 35, "salary" : 15000, "deptno" : 36 }<br/></span>登录后复制
按照薪资降序排列
<span style="font-size: 16px;">> db.emp.find().sort({salary:-1})<br/><br/>{ "_id" : ObjectId("5f9c22445df291fa8194b925"), "empno" : 109, "ename" : "李元静", "sex" : "女", "age" : 35, "salary" : 15000, "deptno" : 36 }<br/>{ "_id" : ObjectId("5f9c219b5df291fa8194b921"), "empno" : 106, "ename" : "李四", "sex" : "男", "age" : 35, "salary" : 12000, "deptno" : 10 }<br/>{ "_id" : ObjectId("5f9c21a75df291fa8194b922"), "empno" : 106, "ename" : "李四", "sex" : "男", "age" : 35, "salary" : 12000, "deptno" : 10 }<br/>{ "_id" : ObjectId("5f9c21855df291fa8194b920"), "empno" : 105, "ename" : "张四", "sex" : "男", "age" : 32, "salary" : 8000, "deptno" : 30 }<br/>{ "_id" : ObjectId("5f9c22185df291fa8194b924"), "empno" : 108, "ename" : "李元芳", "sex" : "男", "age" : 35, "salary" : 8000, "deptno" : 30 }<br/>{ "_id" : ObjectId("5f9c21d85df291fa8194b923"), "empno" : 107, "ename" : "王三", "sex" : "女", "age" : 27, "salary" : 5000, "deptno" : 20 }<br/>{ "_id" : ObjectId("5f9c215f5df291fa8194b91f"), "empno" : 104, "ename" : "李菲菲", "sex" : "女", "age" : 28, "salary" : 4200, "deptno" : 20 }<br/>{ "_id" : ObjectId("5f9c227d5df291fa8194b926"), "empno" : 110, "ename" : "刘静", "sex" : "女", "age" : 25, "salary" : 3500, "deptno" : 10 }<br/>{ "_id" : ObjectId("5f9c20945df291fa8194b91d"), "empno" : 102, "ename" : "张良", "sex" : "男", "age" : 25, "salary" : 3000, "deptno" : 20 }<br/>{ "_id" : ObjectId("5f9c1dfc5df291fa8194b91c"), "empno" : 101, "ename" : "张三", "sex" : "女", "age" : 30, "salary" : 2500, "deptno" : 20 }<br/>{ "_id" : ObjectId("5f9c21055df291fa8194b91e"), "empno" : 103, "ename" : "李明", "sex" : "女", "age" : 30, "salary" : 1800, "deptno" : 30 }<br/>{ "_id" : ObjectId("5f9c1c5b5df291fa8194b91b"), "empno" : 100, "ename" : "admin", "sex" : "男", "age" : 20, "salary" : 800, "deptno" : 10 }<br/></span>登录后复制
15. 查询ename=admin且age=20的员工数据
<span style="font-size: 16px;">> db.emp.find({ename:"admin",age:20})<br/><br/>{ "_id" : ObjectId("5f9c1c5b5df291fa8194b91b"), "empno" : 100, "ename" : "admin", "sex" : "男", "age" : 20, "salary" : 800, "deptno" : 10 }<br/></span>登录后复制
16. 查询前5条数据
<span style="font-size: 16px;">> db.emp.find().limit(5)<br/><br/>{ "_id" : ObjectId("5f9c1c5b5df291fa8194b91b"), "empno" : 100, "ename" : "admin", "sex" : "男", "age" : 20, "salary" : 800, "deptno" : 10 }<br/>{ "_id" : ObjectId("5f9c1dfc5df291fa8194b91c"), "empno" : 101, "ename" : "张三", "sex" : "女", "age" : 30, "salary" : 2500, "deptno" : 20 }<br/>{ "_id" : ObjectId("5f9c20945df291fa8194b91d"), "empno" : 102, "ename" : "张良", "sex" : "男", "age" : 25, "salary" : 3000, "deptno" : 20 }<br/>{ "_id" : ObjectId("5f9c21055df291fa8194b91e"), "empno" : 103, "ename" : "李明", "sex" : "女", "age" : 30, "salary" : 1800, "deptno" : 30 }<br/>{ "_id" : ObjectId("5f9c215f5df291fa8194b91f"), "empno" : 104, "ename" : "李菲菲", "sex" : "女", "age" : 28, "salary" : 4200, "deptno" : 20 }<br/></span>登录后复制
17. 查询10条以后的数据
这里一共12条数据，查询10条以后的数据，结果是两条数据。
<span style="font-size: 16px;">> db.emp.find().skip(10)<br/><br/>{ "_id" : ObjectId("5f9c22445df291fa8194b925"), "empno" : 109, "ename" : "李元静", "sex" : "女", "age" : 35, "salary" : 15000, "deptno" : 36 }<br/>{ "_id" : ObjectId("5f9c227d5df291fa8194b926"), "empno" : 110, "ename" : "刘静", "sex" : "女", "age" : 25, "salary" : 3500, "deptno" : 10 }<br/></span>登录后复制
18. 查询集合中的总数据
一共12条数据
<span style="font-size: 16px;">> db.emp.find().count()<br/><br/>12<br/></span>
登录后复制
查询salary>=5000的员工数量
<span style="font-size: 16px;">> db.emp.find({salary:{$gte:5000}}).count()<br/><br/>6<br/></span>登录后复制
验证（查询查询salary>=5000的员工数据，一共是6条。）
<span style="font-size: 16px;">> db.emp.find({salary:{$gte:5000}})<br/><br/>{ "_id" : ObjectId("5f9c21855df291fa8194b920"), "empno" : 105, "ename" : "张四", "sex" : "男", "age" : 32, "salary" : 8000, "deptno" : 30 }<br/>{ "_id" : ObjectId("5f9c219b5df291fa8194b921"), "empno" : 106, "ename" : "李四", "sex" : "男", "age" : 35, "salary" : 12000, "deptno" : 10 }<br/>{ "_id" : ObjectId("5f9c21a75df291fa8194b922"), "empno" : 106, "ename" : "李四", "sex" : "男", "age" : 35, "salary" : 12000, "deptno" : 10 }<br/>{ "_id" : ObjectId("5f9c21d85df291fa8194b923"), "empno" : 107, "ename" : "王三", "sex" : "女", "age" : 27, "salary" : 5000, "deptno" : 20 }<br/>{ "_id" : ObjectId("5f9c22185df291fa8194b924"), "empno" : 108, "ename" : "李元芳", "sex" : "男", "age" : 35, "salary" : 8000, "deptno" : 30 }<br/>{ "_id" : ObjectId("5f9c22445df291fa8194b925"), "empno" : 109, "ename" : "李元静", "sex" : "女", "age" : 35, "salary" : 15000, "deptno" : 36 }<br/></span>登录后复制
19. 分页查询
按照每页显示5条数据查询，一共12条数据，就要查询3页
<span style="font-size: 16px;">第一页：<br/>> db.emp.find().skip(0).limit(5)<br/><br/>{ "_id" : ObjectId("5f9c1c5b5df291fa8194b91b"), "empno" : 100, "ename" : "admin", "sex" : "男", "age" : 20, "salary" : 800, "deptno" : 10 }<br/>{ "_id" : ObjectId("5f9c1dfc5df291fa8194b91c"), "empno" : 101, "ename" : "张三", "sex" : "女", "age" : 30, "salary" : 2500, "deptno" : 20 }<br/>{ "_id" : ObjectId("5f9c20945df291fa8194b91d"), "empno" : 102, "ename" : "张良", "sex" : "男", "age" : 25, "salary" : 3000, "deptno" : 20 }<br/>{ "_id" : ObjectId("5f9c21055df291fa8194b91e"), "empno" : 103, "ename" : "李明", "sex" : "女", "age" : 30, "salary" : 1800, "deptno" : 30 }<br/>{ "_id" : ObjectId("5f9c215f5df291fa8194b91f"), "empno" : 104, "ename" : "李菲菲", "sex" : "女", "age" : 28, "salary" : 4200, "deptno" : 20 }<br/><br/>第二页：<br/>> db.emp.find().skip(5).limit(5)<br/><br/>{ "_id" : ObjectId("5f9c21855df291fa8194b920"), "empno" : 105, "ename" : "张四", "sex" : "男", "age" : 32, "salary" : 8000, "deptno" : 30 }<br/>{ "_id" : ObjectId("5f9c219b5df291fa8194b921"), "empno" : 106, "ename" : "李四", "sex" : "男", "age" : 35, "salary" : 12000, "deptno" : 10 }<br/>{ "_id" : ObjectId("5f9c21a75df291fa8194b922"), "empno" : 106, "ename" : "李四", "sex" : "男", "age" : 35, "salary" : 12000, "deptno" : 10 }<br/>{ "_id" : ObjectId("5f9c21d85df291fa8194b923"), "empno" : 107, "ename" : "王三", "sex" : "女", "age" : 27, "salary" : 5000, "deptno" : 20 }<br/>{ "_id" : ObjectId("5f9c22185df291fa8194b924"), "empno" : 108, "ename" : "李元芳", "sex" : "男", "age" : 35, "salary" : 8000, "deptno" : 30 }<br/><br/>第三页：<br/>> db.emp.find().skip(10).limit(5)<br/><br/>{ "_id" : ObjectId("5f9c22445df291fa8194b925"), "empno" : 109, "ename" : "李元静", "sex" : "女", "age" : 35, "salary" : 15000, "deptno" : 36 }<br/>{ "_id" : ObjectId("5f9c227d5df291fa8194b926"), "empno" : 110, "ename" : "刘静", "sex" : "女", "age" : 25, "salary" : 3500, "deptno" : 10 }<br/></span>登录后复制
skip的值=（页数-1）* 每页显示数量
skip（N）：表示要查询第N条数据后的数据
20.关键字or的查询方式
查询年龄是30或者年龄是35的员工数据(注意写法)
<span style="font-size: 16px;">> db.emp.find({$or:[{age:30},{age:35}]})<br/><br/>{ "_id" : ObjectId("5f9c1dfc5df291fa8194b91c"), "empno" : 101, "ename" : "张三", "sex" : "女", "age" : 30, "salary" : 2500, "deptno" : 20 }<br/>{ "_id" : ObjectId("5f9c21055df291fa8194b91e"), "empno" : 103, "ename" : "李明", "sex" : "女", "age" : 30, "salary" : 1800, "deptno" : 30 }<br/>{ "_id" : ObjectId("5f9c219b5df291fa8194b921"), "empno" : 106, "ename" : "李四", "sex" : "男", "age" : 35, "salary" : 12000, "deptno" : 10 }<br/>{ "_id" : ObjectId("5f9c21a75df291fa8194b922"), "empno" : 106, "ename" : "李四", "sex" : "男", "age" : 35, "salary" : 12000, "deptno" : 10 }<br/>{ "_id" : ObjectId("5f9c22185df291fa8194b924"), "empno" : 108, "ename" : "李元芳", "sex" : "男", "age" : 35, "salary" : 8000, "deptno" : 30 }<br/>{ "_id" : ObjectId("5f9c22445df291fa8194b925"), "empno" : 109, "ename" : "李元静", "sex" : "女", "age" : 35, "salary" : 15000, "deptno" : 36 }<br/></span>登录后复制
21. 查询第一条数据
<span style="font-size: 16px;">> db.emp.findOne()<br/>{<br/> "_id" : ObjectId("5f9c1c5b5df291fa8194b91b"),<br/> "empno" : 100,<br/> "ename" : "admin",<br/> "sex" : "男",<br/> "age" : 20,<br/> "salary" : 800,<br/> "deptno" : 10<br/>}<br/></span>登录后复制
或
<span style="font-size: 16px;">> db.emp.find().limit(1)<br/><br/>{ "_id" : ObjectId("5f9c1c5b5df291fa8194b91b"), "empno" : 100, "ename" : "admin", "sex" : "男", "age" : 20, "salary" : 800, "deptno" : 10 }<br/></span>登录后复制
22. 查询当前表所在的数据库
<span style="font-size: 16px;">> db.emp.getDB()<br/><br/>company<br/></span>
登录后复制
六、更新数据
更新数据一定要有条件限制，并且需要加上$set否则会全部修改
第一个参数是条件，后面的参数是要修改的数据或者是其他操作，比如批量操作
1. 更新员工李元静的年龄为32岁
<span style="font-size: 16px;">> db.emp.update({ename:"李元静"},{$set:{age:32}})<br/><br/>WriteResult({ "nMatched" : 1, "nUpserted" : 0, "nModified" : 1 })<br/></span>登录后复制
验证(查询姓名是李元静的员工数据)
<span style="font-size: 16px;">> db.emp.find({ename:"李元静"})<br/><br/>{ "_id" : ObjectId("5f9c376a29491ade8d9d3e79"), "empno" : 109, "ename" : "李元静", "sex" : "女", "age" : 32, "salary" : 15000, "deptno" : 36 }<br/></span>登录后复制
2. 更新员工李元静的薪资为1600并且所在部门修改为30
<span style="font-size: 16px;">> db.emp.update({ename:"李元静"},{$set:{salary:1600,deptno:30}})<br/><br/>WriteResult({ "nMatched" : 1, "nUpserted" : 0, "nModified" : 1 })<br/></span>登录后复制
验证(查询姓名是李元静的员工数据)
<span style="font-size: 16px;">> db.emp.find({ename:"李元静"})<br/><br/>{ "_id" : ObjectId("5f9c376a29491ade8d9d3e79"), "empno" : 109, "ename" : "李元静", "sex" : "女", "age" : 32, "salary" : 1600, "deptno" : 30 }<br/></span>登录后复制
3. 批量更新数据
把年龄是35岁的更新为34岁
设置第三个参数：{multi:true}
<span style="font-size: 16px;">> db.emp.update({age:35},{$set:{age:34}},{multi:true})<br/><br/>WriteResult({ "nMatched" : 3, "nUpserted" : 0, "nModified" : 3 })<br/></span>登录后复制
通过db.emp.find()验证所有数据没有年龄为35的员工
4. $inc使用
$inc将一个字段的值增加或者减少
把李元芳的年龄减少1岁，同时薪资加2000
<span style="font-size: 16px;">> db.emp.update({ename:"李元芳"},{$inc:{age:-1,salary:2000}})<br/><br/>WriteResult({ "nMatched" : 1, "nUpserted" : 0, "nModified" : 1 })<br/></span>登录后复制
验证
<span style="font-size: 16px;">> db.emp.find({ename:"李元芳"})<br/><br/>{ "_id" : ObjectId("5f9c22185df291fa8194b924"), "empno" : 108, "ename" : "李元芳", "sex" : "男", "age" : 33, "salary" : 10000, "deptno" : 30 }<br/></span>登录后复制
七、删除操作
1. 删除指定条件的数据
<span style="font-size: 16px;">db.emp.remove({ename:"李元芳"})<br/></span>登录后复制
2. 删除所有数据
<span style="font-size: 16px;">db.emp.remove({})<br/></span>登录后复制
3. 删除集合
<span style="font-size: 16px;">db.emp.drop()<br/></span>
登录后复制
4.删除数据库
<span style="font-size: 16px;">db.dropDatabase()<br/></span>
登录后复制
5. 温馨提示
对数据库数据执行删除操作时，记得加条件！
八、MongoDB数据库索引
MongoDB数据库索引是指对数据库集合中的一列或者多列进行排序的一种结构，可以大大缩减我们在使用数据库查询时候的时间，其用法和关系型数据库一样。
1. 模拟批量插入数据
在使用数据库前，我们创建一个com数据库和users集合，模拟60万条数据
PS:插入60万条数据大概需要5分钟
<span style="font-size: 16px;">> use com<br/>switched to db com<br/>> for(var i=0;i<600000;i++){<br/>... db.users.insert({userNo:i,userName:"张三"+i,age:28,phone:"13000"+i})<br/>... }<br/>WriteResult({ "nInserted" : 1 })<br/></span>登录后复制
验证数据
<span style="font-size: 16px;">> db.users.find().count()<br/>600000<br/></span>
登录后复制
2.无索引查询所耗费时间
<span style="font-size: 16px;">命令： <br/>db.users.find({userNo:599999}).explain("executionStats")<br/></span>登录后复制
<span style="font-size: 16px;">> db.users.find({userNo:599999}).explain("executionStats")<br/>{<br/> "queryPlanner" : {<br/> "plannerVersion" : 1,<br/> "namespace" : "com.users",<br/> "indexFilterSet" : false,<br/> "parsedQuery" : {<br/> "userNo" : {<br/> "$eq" : 599999<br/> }<br/> },<br/> "winningPlan" : {<br/> "stage" : "COLLSCAN",<br/> "filter" : {<br/> "userNo" : {<br/> "$eq" : 599999<br/> }<br/> },<br/> "direction" : "forward"<br/> },<br/> "rejectedPlans" : [ ]<br/> },<br/> "executionStats" : {<br/> "executionSuccess" : true,<br/> "nReturned" : 1,<br/> "executionTimeMillis" : 254,<br/> "totalKeysExamined" : 0,<br/> "totalDocsExamined" : 600000,<br/> "executionStages" : {<br/> "stage" : "COLLSCAN",<br/> "filter" : {<br/> "userNo" : {<br/> "$eq" : 599999<br/> }<br/> },<br/> "nReturned" : 1,<br/> "executionTimeMillisEstimate" : 3,<br/> "works" : 600002,<br/> "advanced" : 1,<br/> "needTime" : 600000,<br/> "needYield" : 0,<br/> "saveState" : 600,<br/> "restoreState" : 600,<br/> "isEOF" : 1,<br/> "direction" : "forward",<br/> "docsExamined" : 600000<br/> }<br/> },<br/> "serverInfo" : {<br/> "host" : "thinkPadE580",<br/> "port" : 27017,<br/> "version" : "4.4.2-rc0",<br/> "gitVersion" : "b5fafa1f87dda6f8773c5a8a1a5e7776d4d94da7"<br/> },<br/> "ok" : 1<br/>}<br/></span>登录后复制
通过"executionTimeMillis" : 254可以知道查询所耗费时间为254毫秒，当然这与计算机配置性能有关。
3. 创建索引
为userNo创建索引
<span style="font-size: 16px;">命令：<br/> db.users.ensureIndex({userNo:1})<br/></span>登录后复制
<span style="font-size: 16px;">> db.users.ensureIndex({userNo:1})<br/>{<br/> "createdCollectionAutomatically" : false,<br/> "numIndexesBefore" : 1,<br/> "numIndexesAfter" : 2,<br/> "ok" : 1<br/>}<br/></span>登录后复制
4. 查询索引
<span style="font-size: 16px;">命令：<br/> db.users.getIndexes()<br/></span>
登录后复制
<span style="font-size: 16px;">> db.users.getIndexes()<br/>[<br/> {<br/> "v" : 2,<br/> "key" : {<br/> "_id" : 1<br/> },<br/> "name" : "_id_"<br/> },<br/> {<br/> "v" : 2,<br/> "key" : {<br/> "userNo" : 1<br/> },<br/> "name" : "userNo_1"<br/> }<br/>]<br/></span>登录后复制
_id为集合默认id索引,userNo是自定义索引
5. 使用索引查询所耗费时间
<span style="font-size: 16px;">> db.users.find({userNo:599999}).explain("executionStats")<br/>{<br/> "queryPlanner" : {<br/> "plannerVersion" : 1,<br/> "namespace" : "com.users",<br/> "indexFilterSet" : false,<br/> "parsedQuery" : {<br/> "userNo" : {<br/> "$eq" : 599999<br/> }<br/> },<br/> "winningPlan" : {<br/> "stage" : "FETCH",<br/> "inputStage" : {<br/> "stage" : "IXSCAN",<br/> "keyPattern" : {<br/> "userNo" : 1<br/> },<br/> "indexName" : "userNo_1",<br/> "isMultiKey" : false,<br/> "multiKeyPaths" : {<br/> "userNo" : [ ]<br/> },<br/> "isUnique" : false,<br/> "isSparse" : false,<br/> "isPartial" : false,<br/> "indexVersion" : 2,<br/> "direction" : "forward",<br/> "indexBounds" : {<br/> "userNo" : [<br/> "[599999.0, 599999.0]"<br/> ]<br/> }<br/> }<br/> },<br/> "rejectedPlans" : [ ]<br/> },<br/> "executionStats" : {<br/> "executionSuccess" : true,<br/> "nReturned" : 1,<br/> "executionTimeMillis" : 84,<br/> "totalKeysExamined" : 1,<br/> "totalDocsExamined" : 1,<br/> "executionStages" : {<br/> "stage" : "FETCH",<br/> "nReturned" : 1,<br/> "executionTimeMillisEstimate" : 0,<br/> "works" : 2,<br/> "advanced" : 1,<br/> "needTime" : 0,<br/> "needYield" : 0,<br/> "saveState" : 0,<br/> "restoreState" : 0,<br/> "isEOF" : 1,<br/> "docsExamined" : 1,<br/> "alreadyHasObj" : 0,<br/> "inputStage" : {<br/> "stage" : "IXSCAN",<br/> "nReturned" : 1,<br/> "executionTimeMillisEstimate" : 0,<br/> "works" : 2,<br/> "advanced" : 1,<br/> "needTime" : 0,<br/> "needYield" : 0,<br/> "saveState" : 0,<br/> "restoreState" : 0,<br/> "isEOF" : 1,<br/> "keyPattern" : {<br/> "userNo" : 1<br/> },<br/> "indexName" : "userNo_1",<br/> "isMultiKey" : false,<br/> "multiKeyPaths" : {<br/> "userNo" : [ ]<br/> },<br/> "isUnique" : false,<br/> "isSparse" : false,<br/> "isPartial" : false,<br/> "indexVersion" : 2,<br/> "direction" : "forward",<br/> "indexBounds" : {<br/> "userNo" : [<br/> "[599999.0, 599999.0]"<br/> ]<br/> },<br/> "keysExamined" : 1,<br/> "seeks" : 1,<br/> "dupsTested" : 0,<br/> "dupsDropped" : 0<br/> }<br/> }<br/> },<br/> "serverInfo" : {<br/> "host" : "thinkPadE580",<br/> "port" : 27017,<br/> "version" : "4.4.2-rc0",<br/> "gitVersion" : "b5fafa1f87dda6f8773c5a8a1a5e7776d4d94da7"<br/> },<br/> "ok" : 1<br/>}<br/></span>登录后复制
用索引查询userNo的值，可以通过"executionTimeMillisEstimate" : 0知道，所耗费的时间为0毫秒，大大缩短了查询速度
6. 删除索引
<span style="font-size: 16px;">命令：<br/> db.users.dropIndex({userNo:1})<br/></span>登录后复制
验证
<span style="font-size: 16px;">> db.users.dropIndex({userNo:1})<br/>{ "nIndexesWas" : 2, "ok" : 1 }<br/></span>登录后复制
可以看出，我们自定义的索引已经删除
7. 复合索引
当要对多个字段进行经常性大量查询的时候，我们可以设置复合索引
<span style="font-size: 16px;">> db.users.ensureIndex({userNo:1,userName:1})<br/>{<br/> "createdCollectionAutomatically" : false,<br/> "numIndexesBefore" : 1,<br/> "numIndexesAfter" : 2,<br/> "ok" : 1<br/>}<br/></span>登录后复制
查看复合索引
<span style="font-size: 16px;">> db.users.getIndexes()<br/>[<br/> {<br/> "v" : 2,<br/> "key" : {<br/> "_id" : 1<br/> },<br/> "name" : "_id_"<br/> },<br/> {<br/> "v" : 2,<br/> "key" : {<br/> "userNo" : 1,<br/> "userName" : 1<br/> },<br/> "name" : "userNo_1_userName_1"<br/> }<br/>]<br/></span>登录后复制
userNo和userName是我们自定义的索引
查询userName:”张三599999”所耗费时间
<span style="font-size: 16px;">> db.users.find({userNo:599999,userName:"张三599999"}).explain("executionStats")))<br/>{<br/> "queryPlanner" : {<br/> "plannerVersion" : 1,<br/> "namespace" : "com.users",<br/> "indexFilterSet" : false,<br/> "parsedQuery" : {<br/> "$and" : [<br/> {<br/> "userName" : {<br/> "$eq" : "张三599999"<br/> }<br/> },<br/> {<br/> "userNo" : {<br/> "$eq" : 599999<br/> }<br/> }<br/> ]<br/> },<br/> "winningPlan" : {<br/> "stage" : "FETCH",<br/> "inputStage" : {<br/> "stage" : "IXSCAN",<br/> "keyPattern" : {<br/> "userNo" : 1,<br/> "userName" : 1<br/> },<br/> "indexName" : "userNo_1_userName_1",<br/> "isMultiKey" : false,<br/> "multiKeyPaths" : {<br/> "userNo" : [ ],<br/> "userName" : [ ]<br/> },<br/> "isUnique" : false,<br/> "isSparse" : false,<br/> "isPartial" : false,<br/> "indexVersion" : 2,<br/> "direction" : "forward",<br/> "indexBounds" : {<br/> "userNo" : [<br/> "[599999.0, 599999.0]"<br/> ],<br/> "userName" : [<br/> "[\"张三599999\", \"张三599999\"]"<br/> ]<br/> }<br/> }<br/> },<br/> "rejectedPlans" : [ ]<br/> },<br/> "executionStats" : {<br/> "executionSuccess" : true,<br/> "nReturned" : 1,<br/> "executionTimeMillis" : 2,<br/> "totalKeysExamined" : 1,<br/> "totalDocsExamined" : 1,<br/> "executionStages" : {<br/> "stage" : "FETCH",<br/> "nReturned" : 1,<br/> "executionTimeMillisEstimate" : 0,<br/> "works" : 2,<br/> "advanced" : 1,<br/> "needTime" : 0,<br/> "needYield" : 0,<br/> "saveState" : 0,<br/> "restoreState" : 0,<br/> "isEOF" : 1,<br/> "docsExamined" : 1,<br/> "alreadyHasObj" : 0,<br/> "inputStage" : {<br/> "stage" : "IXSCAN",<br/> "nReturned" : 1,<br/> "executionTimeMillisEstimate" : 0,<br/> "works" : 2,<br/> "advanced" : 1,<br/> "needTime" : 0,<br/> "needYield" : 0,<br/> "saveState" : 0,<br/> "restoreState" : 0,<br/> "isEOF" : 1,<br/> "keyPattern" : {<br/> "userNo" : 1,<br/> "userName" : 1<br/> },<br/> "indexName" : "userNo_1_userName_1",<br/> "isMultiKey" : false,<br/> "multiKeyPaths" : {<br/> "userNo" : [ ],<br/> "userName" : [ ]<br/> },<br/> "isUnique" : false,<br/> "isSparse" : false,<br/> "isPartial" : false,<br/> "indexVersion" : 2,<br/> "direction" : "forward",<br/> "indexBounds" : {<br/> "userNo" : [<br/> "[599999.0, 599999.0]"<br/> ],<br/> "userName" : [<br/> "[\"张三599999\", \"张三599999\"]"<br/> ]<br/> },<br/> "keysExamined" : 1,<br/> "seeks" : 1,<br/> "dupsTested" : 0,<br/> "dupsDropped" : 0<br/> }<br/> }<br/> },<br/> "serverInfo" : {<br/> "host" : "thinkPadE580",<br/> "port" : 27017,<br/> "version" : "4.4.2-rc0",<br/> "gitVersion" : "b5fafa1f87dda6f8773c5a8a1a5e7776d4d94da7"<br/> },<br/> "ok" : 1<br/>}<br/></span>登录后复制
通过"executionTimeMillis" : 2,可以看出，查询userNo和userName只需要2毫秒
注意：如果在一个集合中，对多个字段设置索引N（N!=1），在使用复合索引查询的时候，要连同第一个索引字段一起查询，如果只单单查询第N个,索引将没有效果。
8.唯一索引
创建唯一索引的条件是，集合中字段的数据不能重复，但在缺省情况下创建是索引均不是唯一索引
由于集合中的age都是一样的值，在给age创建唯一索引的时候会报错
<span style="font-size: 16px;">命令：<br/> > db.users.ensure({age:1},{unique:true})<br/></span>登录后复制
为age创建唯一索引，失败
<span style="font-size: 16px;">> db.users.ensure({age:1},{unique:true})<br/>TypeError: db.users.ensure is not a function :<br/>@(shell):1:1<br/></span>登录后复制
以上是MongoDB 4.X基础教程的详细内容。更多信息请关注PHP中文网其他相关文章！
本站声明
本文内容由网友自发贡献，版权归原作者所有，本站不承担相应法律责任。如您发现有涉嫌抄袭侵权的内容，请联系admin@php.cn
热AI工具
Undresser.AI Undress
人工智能驱动的应用程序，用于创建逼真的裸体照片
AI Clothes Remover
用于从照片中去除衣服的在线人工智能工具。
Undress AI Tool
免费脱衣服图片
Clothoff.io
AI脱衣机
AI Hentai Generator
免费生成ai无尽的。
热门文章
R.E.P.O.能量晶体解释及其做什么（黄色晶体）
1 个月前
By 尊渡假赌尊渡假赌尊渡假赌
R.E.P.O.最佳图形设置
1 个月前
By 尊渡假赌尊渡假赌尊渡假赌
刺客信条阴影：贝壳谜语解决方案
2 周前
By DDD
Windows 11 KB5054979中的新功能以及如何解决更新问题
2 周前
By DDD
威尔R.E.P.O.有交叉游戏吗？
1 个月前
By 尊渡假赌尊渡假赌尊渡假赌
热工具
记事本++7.3.1
好用且免费的代码编辑器
SublimeText3汉化版
中文版，非常好用
禅工作室 13.0.1
功能强大的PHP集成开发环境
Dreamweaver CS6
视觉化网页开发工具
SublimeText3 Mac版
神级代码编辑软件(SublimeText3)
热门话题
navicat过期怎么办
Apr 23, 2024 pm 12:12 PM
解决 Navicat 过期问题的方法包括：续订许可证；卸载并重新安装；禁用自动更新；使用 Navicat Premium Essentials 免费版；联系 Navicat 客户支持。
navicat怎么连mongodb
Apr 24, 2024 am 11:27 AM
要使用 Navicat 连接 MongoDB，您需要：安装 Navicat创建 MongoDB 连接：a. 输入连接名称、主机地址和端口b. 输入认证信息（如果需要）添加 SSL 证书（如果需要）验证连接保存连接
net4.0有什么用
May 10, 2024 am 01:09 AM
.NET 4.0 用于创建各种应用程序，它为应用程序开发人员提供了丰富的功能，包括：面向对象编程、灵活性、强大的架构、云计算集成、性能优化、广泛的库、安全性、可扩展性、数据访问和移动开发支持。
无服务器架构中Java函数与数据库的集成
Apr 28, 2024 am 08:57 AM
在无服务器架构中，Java函数可以与数据库集成，以访问和操作数据库中的数据。关键步骤包括：创建Java函数、配置环境变量、部署函数和测试函数。通过遵循这些步骤，开发人员可以构建复杂的应用程序，无缝访问存储在数据库中的数据。
如何在Debian上配置MongoDB自动扩容
Apr 02, 2025 am 07:36 AM
本文介绍如何在Debian系统上配置MongoDB实现自动扩容，主要步骤包括MongoDB副本集的设置和磁盘空间监控。一、MongoDB安装首先，确保已在Debian系统上安装MongoDB。使用以下命令安装：sudoaptupdatesudoaptinstall-ymongodb-org二、配置MongoDB副本集MongoDB副本集确保高可用性和数据冗余，是实现自动扩容的基础。启动MongoDB服务:sudosystemctlstartmongodsudosys
MongoDB在Debian上的高可用性如何保障
Apr 02, 2025 am 07:21 AM
本文介绍如何在Debian系统上构建高可用性的MongoDB数据库。我们将探讨多种方法，确保数据安全和服务持续运行。关键策略：副本集(ReplicaSet)：利用副本集实现数据冗余和自动故障转移。当主节点出现故障时，副本集会自动选举新的主节点，保证服务的持续可用性。数据备份与恢复：定期使用mongodump命令进行数据库备份，并制定有效的恢复策略，以应对数据丢失风险。监控与报警：部署监控工具（如Prometheus、Grafana）实时监控MongoDB的运行状态，并
navicat能连接mongodb吗
Apr 23, 2024 pm 05:15 PM
是的，Navicat 可以连接到 MongoDB 数据库。具体步骤包括：打开 Navicat 并创建新的连接。选择数据库类型为 MongoDB。输入 MongoDB 主机地址、端口和数据库名称。输入 MongoDB 用户名和密码（如果需要）。单击“连接”按钮。
Navicat查看MongoDB数据库密码的方法
Apr 08, 2025 pm 09:39 PM
直接通过 Navicat 查看 MongoDB 密码是不可能的，因为它以哈希值形式存储。取回丢失密码的方法：1. 重置密码；2. 检查配置文件（可能包含哈希值）；3. 检查代码（可能硬编码密码）。
