MongoDB基操

# 数据库 2024-05-05 20:25 0 42 来源： 云博客

基本概念

  • database 数据库 包含多个collection
    • collection 集合 包含多个文档document（类JSON对象）
      • document 文档 一个文档对象中包含多个key-value键值对

入门

基本命令

  1. show dbs列出全部数据库
  2. db 查看当前数据库
  3. use db_name 切换到/创建数据库db_name
  4. show collections 列出当前库中的所有collection
  5. db.createCollectioin(c_name,{参数文档}) 创建一个名为c_name的collection,至于参数文档以后再说
  6. db.c_name.insert({文档对象}) 往c_name集合中插入数据
  7. db.c_name.find() 查询c_name中的所有document数据
  8. db.c_name.drop() 删除集合
  9. db.dropDatabase()删除数据库

增删改查

增

语法

db.集合名称.insert(document)插入文档时，如果不指定_id参数，MongoDB会为文档分配一个唯一的ObjectId插入方式1db.stu.insert({name:‘gj‘,gender:1})插入方式2s1={_id:‘20160101‘,name:‘hr‘}s1.gender=0db.stu.insert(s1)

操作

> db.createCollection(‘test‘){ "ok" : 1 }> db.test.insert({book:‘红楼梦‘,author:‘曹雪芹‘,roles:[‘贾宝玉‘,‘林黛玉‘,‘薛宝钗‘]})WriteResult({ "nInserted" : 1 })> db.test.insert({name:‘张三‘})WriteResult({ "nInserted" : 1 })> db.test.insert({key:‘value‘,k1:{k2:‘value2‘,k3:‘value3‘}})WriteResult({ "nInserted" : 1 })

删

语法

db.集合名称.remove( <query>, { justOne: <boolean> })只删除匹配到的第一条db.stu.remove({gender:0},{justOne:true})全部删除db.stu.remove({})
  • 参数query:可选，删除的文档的条件
  • 参数justOne:可选，如果设为true或1，则只删除一条，默认false，表示删除多条

操作

> db.test.remove({‘name‘:‘张三‘},{justOne:false})WriteResult({ "nRemoved" : 1 })> db.test.find(){ "_id" : ObjectId("5c419e5afbd19a2f55a0ddd9"), "book" : "红楼梦", "author" : "曹雪芹", "roles" : [ "贾宝玉", "林黛玉", "薛宝钗" ] }{ "_id" : ObjectId("5c419eebfbd19a2f55a0dddb"), "key" : "value", "k1" : { "k2" : "value2", "k3" : "value3" } }>

改

语法

db.集合名称.update( <query>, <update>, {multi: <boolean>})全文档更新db.stu.update({name:‘hr‘},{name:‘mnc‘})指定属性更新，通过操作符$setdb.stu.insert({name:‘hr‘,gender:0})db.stu.update({name:‘hr‘},{$set:{name:‘hys‘}})修改多条匹配到的数据db.stu.update({},{$set:{gender:0}},{multi:true})
  • 参数query:查询条件，类似sql语句update中where部分
  • 参数update:更新操作符，类似sql语句update中set部分
  • 参数multi:可选，默认是false，表示只更新找到的第一条记录，值为true表示把满足条件的文档全部更新

操作

> db.test.update({key:‘value‘},{$set:{key:‘什么鬼‘}},{multi:true})WriteResult({ "nMatched" : 1, "nUpserted" : 0, "nModified" : 1 })> db.test.find(){ "_id" : ObjectId("5c419e5afbd19a2f55a0ddd9"), "book" : "红楼梦", "author" : "曹雪芹", "roles" : [ "贾宝玉", "林黛玉", "薛宝钗" ] }{ "_id" : ObjectId("5c419eebfbd19a2f55a0dddb"), "key" : "什么鬼", "k1" : { "k2" : "value2", "k3" : "value3" } }>

查

语法

db.集合名称.find() 简单列出全部数据db.集合名称.find().pretty() 好看的列出全部数据db.集合名称.findOne() 查一条数据db.集合名称.find({查询参数文档}) 指定参数的查询

操作

> db.test.find({book:‘红楼梦‘}){ "_id" : ObjectId("5c419e5afbd19a2f55a0ddd9"), "book" : "红楼梦", "author" : "曹雪芹", "roles" : [ "贾宝玉", "林黛玉", "薛宝钗" ] }> db.test.find({book:‘红楼梦‘}).pretty(){ "_id" : ObjectId("5c419e5afbd19a2f55a0ddd9"), "book" : "红楼梦", "author" : "曹雪芹", "roles" : [ "贾宝玉", "林黛玉", "薛宝钗" ]}> db.test.findOne({book:‘红楼梦‘}){ "_id" : ObjectId("5c419e5afbd19a2f55a0ddd9"), "book" : "红楼梦", "author" : "曹雪芹", "roles" : [ "贾宝玉", "林黛玉", "薛宝钗" ]}

深入查询

比较运算符

  1. 等于
  2. $lt小于
  3. $lte 小于等于
  4. $gt 大于
  5. $gte 大于等于
  6. $ne not equal
年龄=15> db.student.find({age:15}){ "_id" : ObjectId("5c41d2ce2ac421ae45483f61"), "name" : "micheal", "gender" : 1, "age" : 15 }年龄>15> db.student.find({age:{$gt:15}}){ "_id" : ObjectId("5c41d2f62ac421ae45483f63"), "name" : "alex", "gender" : 1, "age" : 41 }{ "_id" : ObjectId("5c41d30a2ac421ae45483f64"), "name" : "amada", "gender" : 0, "age" : 29 }{ "_id" : ObjectId("5c41d3252ac421ae45483f65"), "name" : "talor", "gender" : 0, "age" : 27 }{ "_id" : ObjectId("5c41d3342ac421ae45483f66"), "name" : "bill", "gender" : 0, "age" : 62 }{ "_id" : ObjectId("5c41d3422ac421ae45483f67"), "name" : "jobs", "gender" : 0, "age" : 46 }年龄>=15> db.student.find({age:{$gte:15}}){ "_id" : ObjectId("5c41d2ce2ac421ae45483f61"), "name" : "micheal", "gender" : 1, "age" : 15 }{ "_id" : ObjectId("5c41d2f62ac421ae45483f63"), "name" : "alex", "gender" : 1, "age" : 41 }{ "_id" : ObjectId("5c41d30a2ac421ae45483f64"), "name" : "amada", "gender" : 0, "age" : 29 }{ "_id" : ObjectId("5c41d3252ac421ae45483f65"), "name" : "talor", "gender" : 0, "age" : 27 }{ "_id" : ObjectId("5c41d3342ac421ae45483f66"), "name" : "bill", "gender" : 0, "age" : 62 }{ "_id" : ObjectId("5c41d3422ac421ae45483f67"), "name" : "jobs", "gender" : 0, "age" : 46 }

逻辑运算符

  1. and 默认
  2. or 使用$or
年龄大于15 and 小于30> db.student.find({age:{$gt:15},age:{$lt:30}}){ "_id" : ObjectId("5c41d2b22ac421ae45483f5f"), "name" : "jack", "gender" : 1, "age" : 13 }{ "_id" : ObjectId("5c41d2c02ac421ae45483f60"), "name" : "rose", "gender" : 0, "age" : 12 }{ "_id" : ObjectId("5c41d2ce2ac421ae45483f61"), "name" : "micheal", "gender" : 1, "age" : 15 }{ "_id" : ObjectId("5c41d2e42ac421ae45483f62"), "name" : "peppa", "gender" : 0, "age" : 4 }{ "_id" : ObjectId("5c41d30a2ac421ae45483f64"), "name" : "amada", "gender" : 0, "age" : 29 }{ "_id" : ObjectId("5c41d3252ac421ae45483f65"), "name" : "talor", "gender" : 0, "age" : 27 }年龄小于15 and gender=1> db.student.find({age:{$lt:15},gender:1}){ "_id" : ObjectId("5c41d2b22ac421ae45483f5f"), "name" : "jack", "gender" : 1, "age" : 13 }name=‘jack‘ or name=‘rose‘> db.student.find({$or:[{name:‘jack‘},{name:‘rose‘}]}){ "_id" : ObjectId("5c41d2b22ac421ae45483f5f"), "name" : "jack", "gender" : 1, "age" : 13 }{ "_id" : ObjectId("5c41d2c02ac421ae45483f60"), "name" : "rose", "gender" : 0, "age" : 12 }(age=12 or age=13) and gender=1> db.student.find({$or:[{age:13},{age:12}],gender:1}){ "_id" : ObjectId("5c41d2b22ac421ae45483f5f"), "name" : "jack", "gender" : 1, "age" : 13 }

范围运算符

  1. $in在某个范围
  2. $nin 不在某个范围
> db.student.find({age:{$in:[15,20]}}){ "_id" : ObjectId("5c41d2ce2ac421ae45483f61"), "name" : "micheal", "gender" : 1, "age" : 15 }相当于age=15 or age=20

正则表达式查询

使用// $regex

name 以j开头的> db.student.find({name:/^j/}){ "_id" : ObjectId("5c41d2b22ac421ae45483f5f"), "name" : "jack", "gender" : 1, "age" : 13 }{ "_id" : ObjectId("5c41d3422ac421ae45483f67"), "name" : "jobs", "gender" : 0, "age" : 46 }name 以m开头的> db.student.find({name:{$regex:‘^m‘}}){ "_id" : ObjectId("5c41d2ce2ac421ae45483f61"), "name" : "micheal", "gender" : 1, "age" : 15 }

自定义查询

使用$where后面写一个函数，返回满足条件的数据

age<15> db.student.find({$where:function(){return this.age<15}}){ "_id" : ObjectId("5c41d2b22ac421ae45483f5f"), "name" : "jack", "gender" : 1, "age" : 13 }{ "_id" : ObjectId("5c41d2c02ac421ae45483f60"), "name" : "rose", "gender" : 0, "age" : 12 }{ "_id" : ObjectId("5c41d2e42ac421ae45483f62"), "name" : "peppa", "gender" : 0, "age" : 4 }

MongoDB函数

skip(number)

在查询结果集的基础上跳过number条数据

limit(number)

在查询结果集的基础上截取number条数据

db.stu.find().skip(5).limit(4)两个连起来正好相当于mysql中的 limit 5,4

sort()

对结果集进行排序

语法 sort({name:1,age:-1,....})1 升序号-1 降序按姓名升序排列 按年龄降序排列> db.student.find().sort({name:1,age:-1}){ "_id" : ObjectId("5c41d2f62ac421ae45483f63"), "name" : "alex", "gender" : 1, "age" : 41 }{ "_id" : ObjectId("5c41d30a2ac421ae45483f64"), "name" : "amada", "gender" : 0, "age" : 29 }{ "_id" : ObjectId("5c41d3342ac421ae45483f66"), "name" : "bill", "gender" : 0, "age" : 62 }按年龄升序排列> db.student.find().sort({age:1}){ "_id" : ObjectId("5c41d2e42ac421ae45483f62"), "name" : "peppa", "gender" : 0, "age" : 4 }{ "_id" : ObjectId("5c41d2c02ac421ae45483f60"), "name" : "rose", "gender" : 0, "age" : 12 }{ "_id" : ObjectId("5c41d2b22ac421ae45483f5f"), "name" : "jack", "gender" : 1, "age" : 13 }

count()

统计结果集中的文档条数

  1. db.c_name.find().count()
  2. db.c_name.count({条件文档对象})
统计gender=1的人数> db.student.find({gender:1}).count()3> db.student.count({gender:1})3

distinct()

对数据进行去重

db.集合名称.distinct(‘去重字段‘,{条件})> db.student.distinct(‘gender‘,{age:{$gt:10}})[ 1, 0 ]

进阶

投影

db.集合名称.find({},{字段名称:1,...})

设置为1代表显示

不设置或设为0代表不显示

_id必须设置为0才不显示

> db.student.find({},{_id:0,name:1}){ "name" : "jack" }{ "name" : "rose" }{ "name" : "micheal" }{ "name" : "peppa" }{ "name" : "alex" }{ "name" : "amada" }{ "name" : "talor" }{ "name" : "bill" }{ "name" : "jobs" }

聚合

db.集合名称.aggregate([{管道:{表达式}}])

aggregate用于计算数据，类sql中的sum()、avg()这些聚合函数的功能

管道

管道作用
$group将文档分组，可用于统计结果
$match过滤数据，只输出符合条件的文档
$project修改输入文档的结构，重命名 增删filed 创建计算结果
$sort排序
$limit $skip类似 mysql limit 2,5
$unwind将数组型字段进行拆分

表达式

表达式:‘$列名‘

处理输入文档并输出

表达式作用
$sum计算总和，$sum:1 同count表示计数
$avg求平均
$min $max最大、最小值
$push在结果文档中插入值到一个数组中
$first $last根据资源文档的排序获取首、尾文档数据
$push的用法> db.student.aggregate([ {$group: {_id:‘$gender‘,name:{$push:‘$name‘}} }]){ "_id" : 0, "name" : [ "rose", "peppa", "amada", "talor", "bill", "jobs" ] }{ "_id" : 1, "name" : [ "jack", "micheal", "alex" ] }> 如果使用$push:‘$$ROOT‘会将整个文档对象添加到name数组中
$group
$group 按gender分组 统计男女同学数 group by _id> db.student.aggregate([ {$group: {_id:‘$gender‘,total:{$sum:1} } }]){ "_id" : 0, "total" : 6 }{ "_id" : 1, "total" : 3 }group by null表示将所有数据分为一组> db.student.aggregate([ {$group: {_id:null,total:{$sum:1},avgAge:{$avg:‘$age‘}} }]){ "_id" : null, "total" : 9, "avgAge" : 27.666666666666668 }
$match
查询年龄大于20的学生> db.student.find({age:{$gt:20}})> db.student.aggregate([{$match:{age:{$gt:20}}}])查询年龄大于20的男生、女生人数> db.student.aggregate([ {$match:{age:{$gt:20}}}, {$group:{_id:‘$gender‘,total:{$sum:1}}}]){ "_id" : 0, "total" : 4 }{ "_id" : 1, "total" : 1 }
$project
> db.student.aggregate([{$project:{_id:0,name:1,age:1}}])> db.student.find({},{_id:0,name:1,age:1})就是find查询的投影查询男生、女生人数，输出人数> db.student.aggregate([{$group:{_id:‘$gender‘,total:{$sum:1}}},{$project:{_id:0,total:1}}]){ "total" : 6 }{ "total" : 3 }
$sort
按age降序排列> db.student.aggregate([{$sort:{age:-1}}]){ "total" : 6 }{ "total" : 3 }查询男生、女生人数，按人数降序> db.student.aggregate([{$group:{_id:‘$gender‘,total:{$sum:1}}},{$sort:{total:-1}}]){ "_id" : 0, "total" : 6 }{ "_id" : 1, "total" : 3 }
$skip $limit

作用就像mysql中的limit x,y ， 两者是有先后顺序的，skip要用在在limit前面。

按age升序排列 limit 0,3> db.student.aggregate([ {$sort:{age:1}}, {$skip:0}, {$limit:3}]){ "_id" : ObjectId("5c41d2e42ac421ae45483f62"), "name" : "peppa", "gender" : 0, "age" : 4 }{ "_id" : ObjectId("5c41d2c02ac421ae45483f60"), "name" : "rose", "gender" : 0, "age" : 12 }{ "_id" : ObjectId("5c41d2b22ac421ae45483f5f"), "name" : "jack", "gender" : 1, "age" : 13 }
$unwind

展开、分开 对某个字段值(值的类型为数组)进行拆分

  • 语法1 db.集合名称.aggregate([{$unwind:‘$字段名称‘}])

  • 语法2

    处理空数组、非数组、无字段、null情况db.集合名称.aggregate([{ $unwind:{ path:‘$字段名称‘, preserveNullAndEmptyArrays:<boolean>#防止数据丢失 }}])
> db.student.insert({name:‘mark‘,gender:1,hobby:[‘smoking‘,‘drinking‘,‘perm‘]})WriteResult({ "nInserted" : 1 })> db.student.aggregate([{$unwind:‘$hobby‘},{$project:{_id:0}}]){ "name" : "mark", "gender" : 1, "hobby" : "smoking" }{ "name" : "mark", "gender" : 1, "hobby" : "drinking" }{ "name" : "mark", "gender" : 1, "hobby" : "perm" }{ "name" : "java", "gender" : 0, "hobby" : "coding" }> db.student.aggregate([{$unwind:{path:‘$hobby‘,preserveNullAndEmptyArrays:true}},{$project:{_id:0}}]){ "name" : "jack", "gender" : 1, "age" : 13 }{ "name" : "rose", "gender" : 0, "age" : 12 }{ "name" : "micheal", "gender" : 1, "age" : 15 }{ "name" : "peppa", "gender" : 0, "age" : 4 }{ "name" : "alex", "gender" : 1, "age" : 41 }{ "name" : "amada", "gender" : 0, "age" : 29 }{ "name" : "talor", "gender" : 0, "age" : 27 }{ "name" : "bill", "gender" : 0, "age" : 62 }{ "name" : "jobs", "gender" : 0, "age" : 46 }{ "name" : "mark", "gender" : 1, "hobby" : "smoking" }{ "name" : "mark", "gender" : 1, "hobby" : "drinking" }{ "name" : "mark", "gender" : 1, "hobby" : "perm" }{ "name" : "java", "gender" : 0, "hobby" : "coding" }{ "name" : "ruby", "gender" : 1, "hobby" : null }

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