MongoDB数据库中,创建、查询、更新、删除操作的对象是集合。
1.查看某个数据库中有哪些集合,在此之前需要使用数据库
C:\Windows\system32>mongo MongoDB shell version: 3.2.10 connecting to: test > db test > show dbs; chengdu 0.004GB first 0.000GB local 0.000GB > use first; switched to db first > show collections; blog col runoob >
命令解释:
mongo ---> 连接数据库, 在执行之前确保MongoDB数据库服务开启了
db ---> 查看当前正在使用的数据库
show dbs --> 查看本地磁盘上那些数据库
use [DatabaseName] --> 使用某个(DatebaseName)数据库,若该数据库不存在,则首先创建数据库再使用
show collections -->查看当前数据库中的集合
2. 向集合中插入一条数据
> show collections; blog col runoob > db first > user = { ‘name‘:‘chengdu‘, ... ‘sex‘ : ‘M‘, ... ‘age‘ : 22 } { "name" : "chengdu", "sex" : "M", "age" : 22 } > db.users.insert(user); WriteResult({ "nInserted" : 1 }) > show collections; blog col runoob users >
首先创建了一个文档对象user,然后再将文档user插入集合users
命令解释:
> user = { ‘name‘:‘chengdu‘,
... ‘sex‘ : ‘M‘,
... ‘age‘ : 22 }
{ "name" : "chengdu", "sex" : "M", "age" : 22 } --> 创建一个文档对象 user
db.users.insert(user) -->向集合users中插入文档user, 如果集合users不存在,则先创建集合, 然后再插入文档对象
3.查询当当前集合中的文档对象,有两个方法 find() 和 findOne()。find()查看所有的文档对象,但在shell中最多显示20个。 findOne()查看第一个文档对象,只返回一个文档对象。
> db.users.find(); { "_id" : ObjectId("584eafa97629396db95535da"), "name" : "chengdu", "sex" : "M", "age" : 22 } > db.users.findOne(); { "_id" : ObjectId("584eafa97629396db95535da"), "name" : "chengdu", "sex" : "M", "age" : 22 } >
具体查询某个文档对象,带参数的查询
> db.users.find({‘name‘:‘chengdu‘}); { "_id" : ObjectId("584eafa97629396db95535da"), "name" : "chengdu", "sex" : "M", "age" : 22 } > db.users.findOne({‘name‘:‘chengdu‘}); { "_id" : ObjectId("584eafa97629396db95535da"), "name" : "chengdu", "sex" : "M", "age" : 22 } >
4.更新集合中的某个文档对象
> user = { ‘name‘ : ‘cd‘, ... ‘sex‘ : ‘M‘, ... ‘age‘ : 22 } { "name" : "cd", "sex" : "M", "age" : 22 } > db.users.update({‘name‘ : ‘chengdu‘}, user); WriteResult({ "nMatched" : 1, "nUpserted" : 0, "nModified" : 1 }) > db.users.find(); { "_id" : ObjectId("584eafa97629396db95535da"), "name" : "cd", "sex" : "M", "age" : 22 } >
使用update语句更新原来集合中name为chengdu的文档对象,更新之后 name变为cd
在文档对象上增加一个键
> user { "name" : "cd", "sex" : "M", "age" : 22 } > user.address = ‘Shanghai‘; Shanghai > user { "name" : "cd", "sex" : "M", "age" : 22, "address" : "Shanghai" } > db.users.update({‘name‘:‘cd‘}, user); WriteResult({ "nMatched" : 1, "nUpserted" : 0, "nModified" : 1 }) > db.users.find(); { "_id" : ObjectId("584eafa97629396db95535da"), "name" : "cd", "sex" : "M", "age" : 22, "address" : "Shanghai" } >
5.删除某个文档对象,使用remove()方法
> user1 = { ‘name‘ : ‘xiaohong‘, ... ‘sex‘ : ‘F‘, ... ‘age‘ : 22, ... ‘address‘ : ‘Beijing‘, ... ‘qq‘ : ‘12345678‘} { "name" : "xiaohong", "sex" : "F", "age" : 22, "address" : "Beijing", "qq" : "12345678" } > db.users.insert(user1); WriteResult({ "nInserted" : 1 }) > db.users.find(); { "_id" : ObjectId("584eafa97629396db95535da"), "name" : "cd", "sex" : "M", "age" : 22, "address" : "Shanghai" } { "_id" : ObjectId("584eb4bd7629396db95535db"), "name" : "xiaohong", "sex" : "F", "age" : 22, "address" : "Beijing", "qq" : "12345678" } > db.users.remove({‘name‘ : ‘xiaohong‘}); WriteResult({ "nRemoved" : 1 }) > db.users.find(); { "_id" : ObjectId("584eafa97629396db95535da"), "name" : "cd", "sex" : "M", "age" : 22, "address" : "Shanghai" } >
首先创建了一个文档对象,该文档对象的键和之前文档对象的键的数目不同,然后再将文档对象插入到集合中,MongoDB的一个集合中可以存储键数目不同的文档对象,即可以插入成功,然后使用remove方法将插入的文档删除。