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MongoDB学习总结

时间：2024-03-13 13:31:17浏览次数：21  
标签：总结 name ObjectId MongoDB age db 学习 gender id

一、数据库基础命令

1、关于database的基础命令

  • 查看所有的数据库：show dbs / show databases
  • 切换数据库：use db_name
  • 查看当前的数据库：db
  • 删除当前的数据库： db.dropDatabase()

2、关于集合的基础命令

  • 不手动创建集合：向不存在的集合中第一次加入数据时，集合会被创建出来
  • 手动创建集合：db.createCollection(name,option)
db.createCollection("stu")

db.createCollection("stu",{capped:true, size:10})

        参数capped：默认值为false表示不设置上限，值为true表示设置上限；

        参数size：当capped值为true时，需要指定此参数，表示上限大小，当文档达到上限时，会将之前的数据覆盖，单位为字节

  • 查看集合：show collections
> use test
> show collections
products
stu
t250
  • 删除集合：db.集合名称.drop()
> db.t250.drop()
true

3、数据类型

3.1、类型

  • Object ID：文档ID (文档：从数据库里取出来的一个一个字典)
  • String：字符串，最常用，必须是有效的UTF-8
  • Boolean：存储一个布尔值，true或false
  • Integer：整数可以是32位或64位，这取决于服务器
  • Double：存储浮点值
  • Arrays：数组或列表，多个值存储到一个键
  • Object：用于嵌入式的文档，即一个值为一个文档
  • Null：存储Null值
  • Timestamp：时间戳，表示从1970-1-1到现在的总秒数
  • Date：存储当前日期或时间的UNIX时间格式

3.2、注意点

  • 创建日期语句如下 ：参数的格式为YYYY-MM-DD
> new Date("2018-01-15")
ISODate("2018-01-15T00:00:00Z")

In [1]:import datetime
In [2]:datetime.datetime.now()
Out[2]:datetime.datetime(2018, 1, 15, 16, 1, 20, 95321)
  • 每个文档都有一个属性，为_id，保证每个文档的唯一性
  • 可以自己去设置_id插入文档，如果没有提供，那么MongoDB为每个文档提供了一个独特的_id，类型为objectID
  • objectID是一个12字节的十六进制数：

        前4个字节为当前时间戳

        接下来3个字节的机器ID

        接下来的2个字节中MongoDB的服务进程id

        最后3个字节是简单的增量值

> db
test
> db.test1000.insert({"name" : "xiaowang", "age" : 10})
WriteResult({"nInserted" : 1})
> db.test1000.find()
{"_id" : ObjectId("5a5c6090018046c04d865339"), "name" : "xiaowang", "age" : 10 }
> db.test1000.insert({name : "xiaohong", age : 18})
WriteResult({"nInserted" : 1})
> db.test1000.find()
{"_id" : ObjectId("5a5c6090018046c04d865339"), "name" : "xiaowang", "age" : 10 }
{"_id" : ObjectId("5a5c60e2018046c04d86533a"), "name" : "xiaohong", "age" : 18 }

二、数据库的增删改

1、插入

  • db.集合名称.insert(document)
db.stu.insert({name:'gj', gender:1})
db.stu.insert({_id:"20170101", name:'gj', gender:1})
  • 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

2、保存

  • db.集合名称.save(document)
> db.test1000.insert({_id:10010, name:"xiaogang", age:30})
WriteResult({"nInserted" : 1})
> db.test1000.find()
{"_id" : ObjectId("5a5c6090018046c04d865339"), "name" : "xiaowang", "age" : 10 }
{"_id" : ObjectId("5a5c60e2018046c04d86533a"), "name" : "xiaohong", "age" : 18 }
{"_id" : 10010, "name" : "xiaogang", "age" : 30 }
> db.test1000.insert({_id:10010, name:"xiaogang", age:40})
WriteResult({
"nInserted" : 0,
"writeError" : {
"code" : 11000,
"errmsg" : "E11000 duplicate key error collection: test.test1000 index：_id_ dup key
}
})
> db.test1000.save({_id:10010, name:"xiaogang", age:40})
WriteResult({ "nMatched" : 1, "nUpserted" : 0, "nModified" : 1 })
> db.test1000.find()
{"_id" : ObjectId("5a5c6090018046c04d865339"), "name" : "xiaowang", "age" : 10 }
{"_id" : ObjectId("5a5c60e2018046c04d86533a"), "name" : "xiaohong", "age" : 18 }
{"_id" : 10010, "name" : "xiaogang", "age" : 40 }

mongodb插入数据

  • db.collecion.insert({}) ：插入数据， _id 存在就报错
  • db.collection.save({})：插入数据， _id 存在会更新

3、简单查询

  • db.集合名称.find()

4、更新

  • db.集合名称.update(<query>, <update>, {multi: <boolean>})

        参数query：查询条件

        参数update：更新操作符

        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

db.stu.update({name : 'hr'}, {name : 'mnc'}) //更新一条
db.stu.update({name : 'hr'}, {$set : {name : 'hys'}}) //更新一条
db.stu.update({} , {$set : {gender : 0}}, {multi : true}) //更新全部
  • 注意：" multi update only works with $ operators "
> db.test1000.update({name : 'xiaowang'}, {name : 'xiaozhao'})
WriteResult({ "nMatched" : 1, "nUpserted" : 0, "nModified" : 1})
> db.test1000.find()
{"_id" : ObjectId("5a5c6090018046c04d865339"), "name" : "xiaozhao" }
{"_id" : ObjectId("5a5c60e2018046c04d86533a"), "name" : "xiaohong", "age" : 18 }
{"_id" : 10010, "name" : "xiaogang", "age" : 40 }
> db.test1000.update({name : 'xiaowang'}, {$set : {name : 'xiaozhang'}})
WriteResult({ "nMatched" : 1, "nUpserted" : 0, "nModified" : 1})
> db.test1000.find()
{"_id" : ObjectId("5a5c6090018046c04d865339"), "name" : "xiaozhao" }
{"_id" : ObjectId("5a5c60e2018046c04d86533a"), "name" : "xiaozhang", "age" : 18 }
{"_id" : 10010, "name" : "xiaogang", "age" : 40 }
> db.test1000.insert({"name" : "xiaozhang", "age" : 40 })
WriteResult({"nInserted" : 1})
> db.test1000.insert({"name" : "xiaozhang", "age" : 22 })
WriteResult({"nInserted" : 1})
> db.test1000.insert({"name" : "xiaozhang", "age" : 18 })
WriteResult({"nInserted" : 1})
> db.test1000.find()
{"_id" : ObjectId("5a5c6090018046c04d865339"), "name" : "xiaozhao" }
{"_id" : ObjectId("5a5c60e2018046c04d86533a"), "name" : "xiaozhang", "age" : 18 }
{"_id" : 10010, "name" : "xiaogang", "age" : 40 }
{"_id" : ObjectId("5a5c6341018046c04d86533b"), "name" : "xiaozhang", "age" : 40 }
{"_id" : ObjectId("5a5c6344018046c04d86533c"), "name" : "xiaozhang", "age" : 22 }
{"_id" : ObjectId("5a5c6347018046c04d86533d"), "name" : "xiaozhang", "age" : 18 }
> db.test1000.update({name : 'xiaozhang'}, {$set : {name : 'xiaohong'}})
WriteResult({ "nMatched" : 1, "nUpserted" : 0, "nModified" : 1})
> db.test1000.find()
{"_id" : ObjectId("5a5c6090018046c04d865339"), "name" : "xiaozhao" }
{"_id" : ObjectId("5a5c60e2018046c04d86533a"), "name" : "xiaohong", "age" : 18 }
{"_id" : 10010, "name" : "xiaogang", "age" : 40 }
{"_id" : ObjectId("5a5c6341018046c04d86533b"), "name" : "xiaozhang", "age" : 40 }
{"_id" : ObjectId("5a5c6344018046c04d86533c"), "name" : "xiaozhang", "age" : 22 }
{"_id" : ObjectId("5a5c6347018046c04d86533d"), "name" : "xiaozhang", "age" : 18 }
> db.test1000.update({name : "xiaozhang"}, {$set : {name : "xiaohong"}}, 
    {multi : true}})
WriteResult({ "nMatched" : 3, "nUpserted" : 0, "nModified" : 3})
> db.test1000.find()
{"_id" : ObjectId("5a5c6090018046c04d865339"), "name" : "xiaozhao" }
{"_id" : ObjectId("5a5c60e2018046c04d86533a"), "name" : "xiaohong", "age" : 18 }
{"_id" : 10010, "name" : "xiaogang", "age" : 40 }
{"_id" : ObjectId("5a5c6341018046c04d86533b"), "name" : "xiaohong", "age" : 40 }
{"_id" : ObjectId("5a5c6344018046c04d86533c"), "name" : "xiaohong", "age" : 22 }
{"_id" : ObjectId("5a5c6347018046c04d86533d"), "name" : "xiaohong", "age" : 18 }
  • db.test1000.update({name : "xiaowang"}, {name : "xiaozhao"})

        把name为xiaowang的数据替换为 {name : "xiaozhao"}

  • db.test1000.update({name : "xiaohong"}, {$set : {name : "xiaozhang"}})

        把name为xiaowang的数据中的name的值更新为xiaozhang

  • db.test1000.update({name : "xiaozhang"}, {$set : {name : "xiaohong"}}, {multi : true})

        {multi : true} 达到更新多条的目的

5、删除

  • db.集合名称.remove(<query>, {justOne: <boolean>})

        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

> db.test1000.remove({name : 'xiaohong'}, {justOne: true})
WriteResult({ "nRemoved" : 1 })
> db.test1000.find()
{"_id" : ObjectId("5a5c6090018046c04d865339"), "name" : "xiaozhao" }
{"_id" : 10010, "name" : "xiaogang", "age" : 40 }
{"_id" : ObjectId("5a5c6341018046c04d86533b"), "name" : "xiaohong", "age" : 40 }
{"_id" : ObjectId("5a5c6344018046c04d86533c"), "name" : "xiaohong", "age" : 22 }
{"_id" : ObjectId("5a5c6347018046c04d86533d"), "name" : "xiaohong", "age" : 18 }
> db.test1000.remove({name : 'xiaohong'})
WriteResult({ "nRemoved" : 3 })
> db.test1000.find()
{"_id" : ObjectId("5a5c6090018046c04d865339"), "name" : "xiaozhao" }
{"_id" : 10010, "name" : "xiaogang", "age" : 40 }

三、数据高级查询

1、数据查询

  • 方法find()： 查询

        db.集合名称.find({条件文档})

  • 方法findOne()：查询，只返回第一个

        db.集合名称.findOne({条件文档})

  • 方法pretty()： 将结果格式化

        db.集合名称.find({条件文档}).pretty()

> db.stu.find() 
{"_id" : ObjectId("5a0401d5507a7101e4eaa600"), "name" : "郭靖", "hometown" : "蒙古", 
    "age" : 20, "gender" : true }
{"_id" : ObjectId("5a0401d5507a7101e4eaa601"), "name" : "黄蓉", "hometown" : "桃花岛", 
    "age" : 18, "gender" :false }
{"_id" : ObjectId("5a0401d5507a7101e4eaa602"), "name" : "华筝", "hometown" : "蒙古", 
    "age" : 18, "gender" : false }
{"_id" : ObjectId("5a0401d5507a7101e4eaa603"), "name" : "黄药师", "hometown" : "桃花岛", 
    "age" : 40, "gender" : true }
{"_id" : ObjectId("5a0401d5507a7101e4eaa604"), "name" : "段誉", "hometown" : "大理", 
    "age" : 16, "gender" : true }
{"_id" : ObjectId("5a0401d5507a7101e4eaa605"), "name" : "段王爷", "hometown" : "大理",
    "age" : 45, "gender" : true }
{"_id" : ObjectId("5a0401d5507a7101e4eaa603"), "name" : "洪七公", "hometown" : "华山", 
    "age" : 18, "gender" : true }
> db.stu.find({age : 20}) 
{"_id" : ObjectId("5a0401d5507a7101e4eaa600"), "name" : "郭靖", "hometown" : "蒙古", 
    "age" : 20, "gender" : true }
> db.stu.find({age : 18}) 
{"_id" : ObjectId("5a0401d5507a7101e4eaa601"), "name" : "黄蓉", "hometown" : "桃花岛", 
    "age" : 18, "gender" :false }
{"_id" : ObjectId("5a0401d5507a7101e4eaa602"), "name" : "华筝", "hometown" : "蒙古", 
    "age" : 18, "gender" : false }
{"_id" : ObjectId("5a0401d5507a7101e4eaa603"), "name" : "洪七公", "hometown" : "华山", 
    "age" : 18, "gender" : true }
> db.stu.findOne({age : 18})
{
    "_id" : ObjectId("5a0401d5507a7101e4eaa601"),
    "name" : "黄蓉",
    "hometown" : "桃花岛"，
    "age" : 18,
    "gender" : false
}
> db.stu.find({age : 18}).pretty()
{
    "_id" : ObjectId("5a0401d5507a7101e4eaa601"),
    "name" : "黄蓉",
    "hometown" : "桃花岛"，
    "age" : 18,
    "gender" : false
}
{
    "_id" : ObjectId("5a0401d5507a7101e4eaa601"),
    "name" : "华筝",
    "hometown" : "蒙古"，
    "age" : 18,
    "gender" : false
}
{
    "_id" : ObjectId("5a0401d5507a7101e4eaa601"),
    "name" : "洪七公",
    "hometown" : "华山"，
    "age" : 18,
    "gender" : true
}

2、比较运算符

  • 等于： 默认是等于判断， 没有运算符
  • 小于：$lt （less than）
  • 小于等于：$lte （less than equal）
  • 大于：$gt （greater than）
  • 大于等于：$gte
  • 不等于：$ne
> db.stu.find({age : {$lte : 18}})
{"_id" : ObjectId("5a0401d5507a7101e4eaa601"), "name" : "黄蓉", "hometown" : "桃花岛", 
    "age" : 18, "gender" :false }
{"_id" : ObjectId("5a0401d5507a7101e4eaa602"), "name" : "华筝", "hometown" : "蒙古", 
    "age" : 18, "gender" : false }
{"_id" : ObjectId("5a0401d5507a7101e4eaa604"), "name" : "段誉", "hometown" : "大理", 
    "age" : 16, "gender" : true }
{"_id" : ObjectId("5a0401d5507a7101e4eaa603"), "name" : "洪七公", "hometown" : "华山", 
    "age" : 18, "gender" : true }
> db.stu.find({age : {$lt : 18}})
{"_id" : ObjectId("5a0401d5507a7101e4eaa604"), "name" : "段誉", "hometown" : "大理", 
    "age" : 16, "gender" : true }

3、范围运算符

  • 使用"$in"， "$nin" 判断是否在某个范围内
db.stu.find({age : {$in : [18, 28]}}) // 查询年龄为18、28的学生

4、逻辑运算符

  • and：在json中写多个条件即可
// 查询年龄大于或等于18，并且性别为true的学生
db.stu.find({age : {$gte : 18}, gender : true})
  • or: 使用"$or"，值为数组，数组中每个元素为json
// 查询年龄大于18，或性别为false的学生
db.stu.find({$or : [{age : {$gt : 18}}, {gender : false}]}) 
db.stu.find({$or : [{age : {$gte : 18}}, {gender : true}], name : 'gj'}) //

5、支持正则表达式

  • 使用"//"或"$regex"编写正则表达式
db.stu.find({name : /^⻩/}) // 查询姓黄的学生
db.stu.find({name : {$regex:'^⻩'}}) // 查询姓黄的学生
> db.products.find()
{ "_id" : 100, "sku" : "abc123", "description" : "Single line description." }
{ "_id" : 101, "sku" : "abc789", "description" : "First line\nSecond line" }
{ "_id" : 102, "sku" : "xyz456", "description" : "Many spaces before line" }
{ "_id" : 103, "sku" : "xyz789", "description" : "Multiple\nline description" }
{ "_id" : 104, "sku" : "abc123", "description" : "Single line description." }
> db.products.find({sku : /^abd/})
{ "_id" : 100, "sku" : "abc123", "description" : "Single line description." }
{ "_id" : 101, "sku" : "abc789", "description" : "First line\nSecond line" }
{ "_id" : 104, "sku" : "abc123", "description" : "Single line description." }
> db.products.find({sku : {$regex : "789$"}})
{ "_id" : 101, "sku" : "abc789", "description" : "First line\nSecond line" }
{ "_id" : 103, "sku" : "xyz789", "description" : "Multiple\nline description" }

6、limit和skip

  • ⽅法limit()：⽤于读取指定数量的⽂档

        db.集合名称.find().limit(NUMBER)

db.stu.find().limit(2) // 查询2条学⽣信息
  • ⽅法skip()：⽤于跳过指定数量的⽂档

        db.集合名称.find().skip(NUMBER)

db.stu.find().skip(2)
> db.products.find().limit(2)
{ "_id" : 100, "sku" : "abc123", "description" : "Single line description." }
{ "_id" : 101, "sku" : "abc789", "description" : "First line\nSecond line" }
> db.products.find().skip(2)
{ "_id" : 102, "sku" : "xyz456", "description" : "Many spaces before line" }
{ "_id" : 103, "sku" : "xyz789", "description" : "Multiple\nline description" }
{ "_id" : 104, "sku" : "abc123", "description" : "Single line description." }
> db.products.find().skip(2).limit(2)
{ "_id" : 102, "sku" : "xyz456", "description" : "Many spaces before line" }
{ "_id" : 103, "sku" : "xyz789", "description" : "Multiple\nline description" }

7、自定义查询

  • 使用"$where"后⾯写⼀个函数，返回满足条件的数据
db.stu.find({
    $where:function() {
        return this.age > 30;}
}) // 查询年龄大于30的学⽣
> db.stu.find({$where : function(){return this.age <= 18}})
{"_id" : ObjectId("5a0401d5507a7101e4eaa601"), "name" : "黄蓉", "hometown" : "桃花岛", 
    "age" : 18, "gender" :false }
{"_id" : ObjectId("5a0401d5507a7101e4eaa602"), "name" : "华筝", "hometown" : "蒙古", 
    "age" : 18, "gender" : false }
{"_id" : ObjectId("5a0401d5507a7101e4eaa604"), "name" : "段誉", "hometown" : "大理", 
    "age" : 16, "gender" : true }
{"_id" : ObjectId("5a0401d5507a7101e4eaa603"), "name" : "洪七公", "hometown" : "华山", 
    "age" : 18, "gender" : true }
> db.stu.find({age : {$lt : 18}})
{"_id" : ObjectId("5a0401d5507a7101e4eaa604"), "name" : "段誉", "hometown" : "大理", 
    "age" : 16, "gender" : true }

8、投影

  • 在查询到的返回结果中，只选择必要的字段
db.集合名称.find({},{字段名称:1,...})

参数为字段与值，值为1表示显示
特殊： 对于_id列默认是显示的，如果不显示需要明确设置为0

> db.stu.find({age : {$gt : 18}}, {name : 1})
{"_id" : ObjectId("5a0401d5507a7101e4eaa600"), "name" : "郭靖" }
{"_id" : ObjectId("5a0401d5507a7101e4eaa603"), "name" : "黄药师" }
{"_id" : ObjectId("5a0401d5507a7101e4eaa605"), "name" : "段王爷" }
> db.stu.find({age : {$gt : 18}}, {name : 1, hometown : 1})
{"_id" : ObjectId("5a0401d5507a7101e4eaa600"), "name" : "郭靖", 
    "hometown" : "蒙古" }
{"_id" : ObjectId("5a0401d5507a7101e4eaa603"), "name" : "黄药师", 
    "hometown" : "桃花岛" }
{"_id" : ObjectId("5a0401d5507a7101e4eaa605"), "name" : "段王爷", 
    "hometown" : "大理" }
> db.stu.find({age : {$gt : 18}}, {name : 1, _id : 0})
{"name" : "郭靖" }
{"name" : "黄药师" }
{"name" : "段王爷" }

9、排序

  • 方法sort()，用于对集合进行排序
db.集合名称.find().sort({字段:1,...})

参数1为升序排列
参数-1为降序排列

> db.stu.find() 
{"_id" : ObjectId("5a0401d5507a7101e4eaa600"), "name" : "郭靖", "hometown" : "蒙古", 
    "age" : 20, "gender" : true }
{"_id" : ObjectId("5a0401d5507a7101e4eaa601"), "name" : "黄蓉", "hometown" : "桃花岛", 
    "age" : 18, "gender" :false }
{"_id" : ObjectId("5a0401d5507a7101e4eaa602"), "name" : "华筝", "hometown" : "蒙古", 
    "age" : 18, "gender" : false }
{"_id" : ObjectId("5a0401d5507a7101e4eaa603"), "name" : "黄药师", "hometown" : "桃花岛", 
    "age" : 40, "gender" : true }
{"_id" : ObjectId("5a0401d5507a7101e4eaa604"), "name" : "段誉", "hometown" : "大理", 
    "age" : 16, "gender" : true }
{"_id" : ObjectId("5a0401d5507a7101e4eaa605"), "name" : "段王爷", "hometown" : "大理", 
    "age" : 45, "gender" : true }
{"_id" : ObjectId("5a0401d5507a7101e4eaa603"), "name" : "洪七公", "hometown" : "华山", 
    "age" : 18, "gender" : true }
> db.stu.find.sort({age : 1})
{"_id" : ObjectId("5a0401d5507a7101e4eaa604"), "name" : "段誉", "hometown" : "大理", 
    "age" : 16, "gender" : true }
{"_id" : ObjectId("5a0401d5507a7101e4eaa601"), "name" : "黄蓉", "hometown" : "桃花岛", 
    "age" : 18, "gender" :false }
{"_id" : ObjectId("5a0401d5507a7101e4eaa602"), "name" : "华筝", "hometown" : "蒙古", 
    "age" : 18, "gender" : false }
{"_id" : ObjectId("5a0401d5507a7101e4eaa603"), "name" : "洪七公", "hometown" : "华山", 
    "age" : 18, "gender" : true }
{"_id" : ObjectId("5a0401d5507a7101e4eaa600"), "name" : "郭靖", "hometown" : "蒙古", 
    "age" : 20, "gender" : true }
{"_id" : ObjectId("5a0401d5507a7101e4eaa603"), "name" : "黄药师", "hometown" : "桃花岛", 
    "age" : 40, "gender" : true }
{"_id" : ObjectId("5a0401d5507a7101e4eaa605"), "name" : "段王爷", "hometown" : "大理", 
    "age" : 45, "gender" : true }
> db.stu.find.sort({age : -1})
{"_id" : ObjectId("5a0401d5507a7101e4eaa605"), "name" : "段王爷", "hometown" : "大理", "age" : 45, "gender" : true }
{"_id" : ObjectId("5a0401d5507a7101e4eaa603"), "name" : "黄药师", "hometown" : "桃花岛", 
    "age" : 40, "gender" : true }
{"_id" : ObjectId("5a0401d5507a7101e4eaa600"), "name" : "郭靖", "hometown" : "蒙古", 
    "age" : 20, "gender" : true }
{"_id" : ObjectId("5a0401d5507a7101e4eaa601"), "name" : "黄蓉", "hometown" : "桃花岛", 
    "age" : 18, "gender" :false }
{"_id" : ObjectId("5a0401d5507a7101e4eaa602"), "name" : "华筝", "hometown" : "蒙古", 
    "age" : 18, "gender" : false }
{"_id" : ObjectId("5a0401d5507a7101e4eaa603"), "name" : "洪七公", "hometown" : "华山", 
    "age" : 18, "gender" : true }
{"_id" : ObjectId("5a0401d5507a7101e4eaa604"), "name" : "段誉", "hometown" : "大理", 
    "age" : 16, "gender" : true }
> db.stu.find.sort({age : -1, gender : -1})
{"_id" : ObjectId("5a0401d5507a7101e4eaa605"), "name" : "段王爷", "hometown" : "大理", 
    "age" : 45, "gender" : true }
{"_id" : ObjectId("5a0401d5507a7101e4eaa603"), "name" : "黄药师", "hometown" : "桃花岛", 
    "age" : 40, "gender" : true }
{"_id" : ObjectId("5a0401d5507a7101e4eaa600"), "name" : "郭靖", "hometown" : "蒙古", 
    "age" : 20, "gender" : true }
{"_id" : ObjectId("5a0401d5507a7101e4eaa603"), "name" : "洪七公", "hometown" : "华山", 
    "age" : 18, "gender" : true }
{"_id" : ObjectId("5a0401d5507a7101e4eaa601"), "name" : "黄蓉", "hometown" : "桃花岛", 
    "age" : 18, "gender" :false }
{"_id" : ObjectId("5a0401d5507a7101e4eaa602"), "name" : "华筝", "hometown" : "蒙古", 
    "age" : 18, "gender" : false }
{"_id" : ObjectId("5a0401d5507a7101e4eaa604"), "name" : "段誉", "hometown" : "大理", 
    "age" : 16, "gender" : true }
> db.stu.find({age : {$gt : 18}}).sort({age : 1})
{"_id" : ObjectId("5a0401d5507a7101e4eaa600"), "name" : "郭靖", "hometown" : "蒙古", 
    "age" : 20, "gender" : true }
{"_id" : ObjectId("5a0401d5507a7101e4eaa603"), "name" : "黄药师", "hometown" : "桃花岛", 
    "age" : 40, "gender" : true }
{"_id" : ObjectId("5a0401d5507a7101e4eaa605"), "name" : "段王爷", "hometown" : "大理", 
    "age" : 45, "gender" : true }

10、统计个数

  • 方法count()⽤于统计结果集中文档条数
> db.stu.find.count()
7
> db.stu.find({age : {$gt : 18}}).count()
3
> db.stu.find({age : {$gte : 18}}).count()
6
> db.stu.count()
7
> db.stu.count({age : {$lte : 18}})
4

11、消除重复

  • 方法distinct()对数据进行去重
> db.stu.distinct("hometown")
["蒙古", "桃花岛", "大理", "华山"]
> db.stu.distinct("age")
[20, 18, 40, 16, 45]
> db.stu.distinct("hometown", {age : {$gt : 20}})
["桃花岛", "大理"]

四、数据的备份和恢复

1、备份

  • 语法
mongodump -h dbhost -d dbname -o dbdirectory

-h： 服务器地址， 也可以指定端口号

-d： 需要备份的数据库名称

-o： 备份的数据存放位置， 此目录中存放着备份出来的数据

mongodump -h 192.168.196.128:27017 -d test1 -o ~/Desktop/test1bak

2、恢复

  • 语法
mongorestore -h dbhost -d dbname --dir dbdirectory

-h： 服务器地址

-d： 需要恢复的数据库实例

--dir： 备份数据所在位置

mongorestore -h 192.168.196.128:27017 -d test2 --dir ~/Desktop/test1bak/test1

五、聚合和管道

1、聚合aggregate

  • 聚合(aggregate)是基于数据处理的聚合管道，每个文档通过一个由多个阶段（stage）组成的管道，可以对每个阶段的管道进行分组、过滤等功能，然后经过一系列的处理，输出相应的结果。
db.集合名称.aggregate({管道 : {表达式}})

2、常用管道

在mongodb中，文档处理完毕后，通过管道进行下一次处理

常用管道如下：

$group： 将集合中的文档分组，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，如重命名、增加、删除字段、创建计算结果

$sort： 将输⼊文档排序后输出

$limit： 限制聚合管道返回的文档数

$skip： 跳过指定数量的文档， 并返回余下的文档

$unwind： 将数组类型的字段进行拆分

3、表达式

处理输入文档并输出

  • 语法：表达式: '$列名'

常用表达式:

$sum： 计算总和，$sum:1 表示以一倍计数

$avg： 计算平均值

$min： 获取最小值

$max： 获取最大值

$push： 在结果文档中插⼊值到一个数组中

$first： 根据资源文档的排序获取第一个文档数据

$last： 根据资源文档的排序获取最后一个文档数据

4、聚合之group

  • $group
> db.stu.find() 
{"_id" : ObjectId("5a0401d5507a7101e4eaa600"), "name" : "郭靖", "hometown" : "蒙古", 
    "age" : 20, "gender" : true }
{"_id" : ObjectId("5a0401d5507a7101e4eaa601"), "name" : "黄蓉", "hometown" : "桃花岛", 
    "age" : 18, "gender" :false }
{"_id" : ObjectId("5a0401d5507a7101e4eaa602"), "name" : "华筝", "hometown" : "蒙古", 
    "age" : 18, "gender" : false }
{"_id" : ObjectId("5a0401d5507a7101e4eaa603"), "name" : "黄药师", "hometown" : "桃花岛", 
    "age" : 40, "gender" : true }
{"_id" : ObjectId("5a0401d5507a7101e4eaa604"), "name" : "段誉", "hometown" : "大理", 
    "age" : 16, "gender" : true }
{"_id" : ObjectId("5a0401d5507a7101e4eaa605"), "name" : "段王爷", "hometown" : "大理", 
    "age" : 45, "gender" : true }
{"_id" : ObjectId("5a0401d5507a7101e4eaa603"), "name" : "洪七公", "hometown" : "华山", 
    "age" : 18, "gender" : true }
> db.stu.aggregate(
        {$group : {_id : "$gender"}}
    )
{"_id" : false}
{"_id" : true}
> db.stu.aggregate(
        {$group : {_id : "$gender", count : {$sum : 1}}}
    )
{ "_id" : false, "count" : 2}
{ "_id" : true, "count" : 5}
> db.stu.aggregate(
        {$group : {_id : "$gender", count : {$sum : 1}, avg_age : {$avg : "$age"}}}
    )
{ "_id" : false, "count" : 2, "avg_age" : 18}
{ "_id" : true, "count" : 5, "avg_age" : 27.8}
> db.stu.aggregate(
        {$group : {_id : "$hometown", mean_age : {$avg : "$age"}}}
    )
{ "_id" : "华山"， "mean_age" : 18}
{ "_id" : "大理"， "mean_age" : 30.5}
{ "_id" : "桃花岛"， "mean_age" : 29}
{ "_id" : "蒙古"， "mean_age" : 19}
  • Group by null

        将集合中所有文档分为一组

> db.stu.aggragate(
{$group : {_id : null, count : {$sum : 1}, mean_age : {$avg : "$age"}}}
)
{ "_ic" : null, "count" : 7, "mean_age" : 25}
  • $group的注意点

$group 对应的字典中有几个键，结果中就有几个键

分组依据需要放到 _id 后面

取不同的字段的值需要使用$, $gender , $age

取字典嵌套的字典中的值的时候 $_id.country

能同时按照多个键进行分组 {$group:{_id:{country:"$country",province:"$province"}}}

结果是： {_id:{country:"",province:""}

  • 透视数据
  • 练习
> db.tv3.find()
{ "_id" : ObjectId("5a07ff40699a3774b04612c1"), "country" : "china", 
    "province" : "sh", "userid" : "a" }  
{ "_id" : ObjectId("5a07ff40699a3774b04612c2"), "country" : "china", 
    "province" : "sh", "userid" : "b" }  
{ "_id" : ObjectId("5a07ff40699a3774b04612c3"), "country" : "china", 
    "province" : "sh", "userid" : "a" }  
{ "_id" : ObjectId("5a07ff40699a3774b04612c4"), "country" : "china", 
    "province" : "sh", "userid" : "c" }  
{ "_id" : ObjectId("5a07ff40699a3774b04612c5"), "country" : "china", 
    "province" : "bj", "userid" : "da" }  
{ "_id" : ObjectId("5a07ff40699a3774b04612c6"), "country" : "china", 
    "province" : "bj", "userid" : "fa" }
> db.tv3.aggregate(
        {$group : {_id : {country : '$country', province :'$province'}}}
)
{ "_id" : { "country" : "china", "province" : "bj" } }
{ "_id" : { "country" : "china", "province" : "sn" } }
> db.tv3.aggregate(
        {$group : {_id : {country : '$country', province :'$province', userid : '$userid'}}}
)
{ "_id" : { "country" : "china", "province" : "bj", "userid" : "fa" } }
{ "_id" : { "country" : "china", "province" : "bj", "userid" : "da" } }
{ "_id" : { "country" : "china", "province" : "sh", "userid" : "b" } }
{ "_id" : { "country" : "china", "province" : "sh", "userid" : "c" } }
{ "_id" : { "country" : "china", "province" : "sh", "userid" : "a" } }
> db.tv3.aggregate(
        {$group : {_id : {country : '$country', province :'$province', 
    userid : '$userid' } } },
        {$group : {_id : {country : '$_id.country', province : '$_id.province'} } }
)
{ "_id" : { "country" : "china", "province" : "sh" } }
{ "_id" : { "country" : "china", "province" : "bj" } }
> db.tv3.aggregate(
        {$group : {_id : {country : '$country', province :'$province', 
    userid : '$userid' } } },
        {$group : {_id : {country : '$_id.country', province : '$_id.province'}, 
    count : {$sum : 1 } } }
)
{ "_id" : { "country" : "china", "province" : "sh" }, "conut" : 3 }
{ "_id" : { "country" : "china", "province" : "bj" }, "conut" : 2 }
// 统计出每个country/province下的userid的数量（同一个userid只统计一次）
> db.tv3.aggregate(
        {$group : {_id : {country : '$country', province :'$province', 
    userid : '$userid' } } },
        {$group : {_id : {country : '$_id.country', province : '$_id.province'}, 
    count : {$sum : 1 } } }, 
        {$project : {country : '$_id.country', province : '$_id.province', 
    count : 1, _id : 0 } }
)
{ "conut" : 3, "country" : "china", "province" : "sh" }
{ "conut" : 2, "country" : "china", "province" : "bj" }
>
  • $match

        用于过滤数据，只输出符合条件的文档

        使用MongoDB的标准查询操作

match是管道命令，能将结果交给后一个管道，但是find不可以

> db.stu.aggregate(
{$match : {age : {$gt : 20}}},
{$group : {_id : "$gender", count : {$sum : 1}}},
{$project : {_id : 0, gender : "$_id", count : 1}}
)
{ "count" : 2, "gender" : true}
> db.stu.aggregate(
{$match : {age : {$gte : 18}}},
{$group : {_id : "$gender", count : {$sum : 1}}},
{$project : {_id : 0, gender : "$_id", count : 1}}
)
{ "count" : 2, "gender" : false}
{ "count" : 4, "gender" : true}
> db.stu.aggregate(
{$match : {$or : [{age : {$gte : 20}}, {hometown : 
    {$in : ["蒙古", "大理"] } } ] } }
{$group : {_id : "$gender", count : {$sum : 1}}},
{$project : {_id : 0, gender : "$_id", count : 1}}
)
{ "count" : 1, "gender" : false}
{ "count" : 4, "gender" : true}
  • $project

        修改输入文档的结构，如重命名、增加、删除字段、创建计算结果

> db.stu.aggregate(
{$group : {_id : "$gender", count : {$sum : 1}, avg_age : {$avg : "$age"}}},
{$project : {gender : "$_id", count : "$count", avg_age : "$avg_age"}}
)
{"_id" : false, "gender" : false, "count" : 2, "avg_age": 18}
{"_id" : true, "gender" : true, "count" : 5, "avg_age": 27.8}
> db.stu.aggregate(
{$group : {_id : "$gender", count : {$sum : 1}, avg_age : {$avg : "$age"}}},
{$project : {gender : "$_id", count : 1, avg_age : "$avg_age", _id : 0}}
)
{"count" : 2, "gender" : false, "avg_age": 18}
{"count" : 5, "gender" : true, "avg_age": 27.8}
  • $sort

        将输入文档排序后输出

> db.stu.find() 
{"_id" : ObjectId("5a0401d5507a7101e4eaa600"), "name" : "郭靖", "hometown" : "蒙古", 
    "age" : 20, "gender" : true }
{"_id" : ObjectId("5a0401d5507a7101e4eaa601"), "name" : "黄蓉", "hometown" : "桃花岛", 
    "age" : 18, "gender" :false }
{"_id" : ObjectId("5a0401d5507a7101e4eaa602"), "name" : "华筝", "hometown" : "蒙古", 
    "age" : 18, "gender" : false }
{"_id" : ObjectId("5a0401d5507a7101e4eaa603"), "name" : "黄药师", "hometown" : "桃花岛", 
    "age" : 40, "gender" : true }
{"_id" : ObjectId("5a0401d5507a7101e4eaa604"), "name" : "段誉", "hometown" : "大理", 
    "age" : 16, "gender" : true }
{"_id" : ObjectId("5a0401d5507a7101e4eaa605"), "name" : "段王爷", "hometown" : "大理", 
    "age" : 45, "gender" : true }
{"_id" : ObjectId("5a0401d5507a7101e4eaa603"), "name" : "洪七公", "hometown" : "华山", 
    "age" : 18, "gender" : true }
> db.stu.aggregate(
       {$group : {_id : "$gender", count : {$sum : 1}}}, {$sort : {count : -1}}
)
{ "_id" : true, "count" : 5}
{ "_id" : false, "count" : 2}
  • $limit和$skip

        $limit ： 限制聚合管道返回的文档数

> db.stu.aggregate({$limit : 2})
{"_id" : ObjectId("5a0401d5507a7101e4eaa600"), "name" : "郭靖", "hometown" : "蒙古", 
    "age" : 20, "gender" : true }
{"_id" : ObjectId("5a0401d5507a7101e4eaa601"), "name" : "黄蓉", "hometown" : "桃花岛", 
    "age" : 18, "gender" :false }

        $skip ： 跳过指定数量的文档，并返回余下的文档

> db.stu.aggregate({$skip : 2})
{"_id" : ObjectId("5a0401d5507a7101e4eaa602"), "name" : "华筝", "hometown" : "蒙古", 
    "age" : 18, "gender" : false }
{"_id" : ObjectId("5a0401d5507a7101e4eaa603"), "name" : "黄药师", "hometown" : "桃花岛", 
    "age" : 40, "gender" : true }
{"_id" : ObjectId("5a0401d5507a7101e4eaa604"), "name" : "段誉", "hometown" : "大理", 
    "age" : 16, "gender" : true }
{"_id" : ObjectId("5a0401d5507a7101e4eaa605"), "name" : "段王爷", "hometown" : "大理", 
    "age" : 45, "gender" : true }
{"_id" : ObjectId("5a0401d5507a7101e4eaa603"), "name" : "洪七公", "hometown" : "华山", 
    "age" : 18, "gender" : true }
> db.stu.aggregate({$skip : 2}, {$limit : 2})
{"_id" : ObjectId("5a0401d5507a7101e4eaa602"), "name" : "华筝", "hometown" : "蒙古", 
    "age" : 18, "gender" : false }
{"_id" : ObjectId("5a0401d5507a7101e4eaa603"), "name" : "黄药师", "hometown" : "桃花岛", 
    "age" : 40, "gender" : true }
  • $unwind

        将文档中的某一个数组类型字段拆分成多条，每条包含数组中的一个值

db.集合名称.aggregate({$unwind : "$字段名称"})
> db.t2.find()
{ "_id" : 1, "item" : 't-shirt', "size" : ['S', 'M', 'L']}
> db.t2.aggregate({$unwind : "$size"})
{ "_id" : 1, "item" : "t-shirt", "size" : "S" }
{ "_id" : 1, "item" : "t-shirt", "size" : "M" }
{ "_id" : 1, "item" : "t-shirt", "size" : "L" }
// 数据库中有一条数据：{"username":"Alex","tags": ['C#','Java','C++']}，
// 如何获取该tag列表的长度
> db.t2.insert({"username":"Alex","tags": ['C#','Java','C++']})
WriteResult({ "nInserted" : 1})
> db.t2.find()
{ "_id" : 1, "item" : 't-shirt', "size" : ['S', 'M', 'L']}
{ "_id" : Object("5a604b132b127e7d06559e98"), "username" : "Alex", 
    "tags": ['C#', 'Java', 'C++'] }
> db.t2.aggregate(
        {$match : {username : "Alex"}},
        {$unwind : "$tags"}
)
{ "_id" : Object("5a604b132b127e7d06559e98"), "username" : "Alex", "tags" : 'C#' }
{ "_id" : Object("5a604b132b127e7d06559e98"), "username" : "Alex", "tags" : 'Java' }
{ "_id" : Object("5a604b132b127e7d06559e98"), "username" : "Alex", "tags" : 'C++' }
> db.t2.aggregate(
        {$match : {username : "Alex"}},
        {$unwind : "$tags"},
        {$group : {_id : null, sum : {$sum : 1}}}
)
{ "_id" : null, "sum" : 3 }

属性preserveNullAndEmptyArrays值为false表示丢弃属性值为空的文档

属性preserveNullAndEmptyArrays值为true表示保留属性值为空的文档

> db.t3.find()
{ "_id" : 1, "item" : "a", "size": [ "S", "M", "L"] }
{ "_id" : 2, "item" : "b", "size" : [ ] }
{ "_id" : 3, "item" : "c", "size": "M" }
{ "_id" : 4, "item" : "d" }
{ "_id" : 5, "item" : "e", "size" : null }
> db.t3.aggregate(
        {$unwind : "$size"}
)
{ "_id" : 1, "item" : "a", "size": "S" }
{ "_id" : 1, "item" : "a", "size": "M" }
{ "_id" : 1, "item" : "a", "size": "L" }
{ "_id" : 3, "item" : "c", "size": "M" }
> db.t3.aggregate(
        {$unwind : 
            {path : "$size"}
        }
)
{ "_id" : 1, "item" : "a", "size": "S" }
{ "_id" : 1, "item" : "a", "size": "M" }
{ "_id" : 1, "item" : "a", "size": "L" }
{ "_id" : 3, "item" : "c", "size": "M" }
> db.t3.aggregate(
        {$unwind : 
            {path : "$size",
             preserveNullAndEmptyArrays : true
            }
        }
)
{ "_id" : 1, "item" : "a", "size": "S" }
{ "_id" : 1, "item" : "a", "size": "M" }
{ "_id" : 1, "item" : "a", "size": "L" }
{ "_id" : 2, "item" : "b" }
{ "_id" : 3, "item" : "c", "size": "M" }
{ "_id" : 4, "item" : "d" }
{ "_id" : 5, "item" : "e", "size" : null }

六、索引

1、创建索引

  • 索引：以提升查询速度
db.集合.ensureIndex({属性 : 1}) // 1表示升序， -1表示降
> db.t255.find().count()
100000
> db.t255.find({ name : "test10000"})
{ "_id" : ObjectId("5a6050132b127e7d0655c5a9"), "name" : "test10000", "age" : 10000 }
> db.t255.find({name : "test10000"}).explain("executionStats")
"executionStats" : {
        "executionSuccess" : true,
        "nReturned" : 1,
        "executionTimeMillis" : 34,
        "totalKeysExamined" : 0
}
> db.t255.ensureIndex({name : 1})
{
        "createdCollectionAutomatically" : false,
        "numIndexesBefore" : 1,
        "numIndexesAfter" : 2,
        "ok" : 1
}
> db.t255.find({name : "test10000"}).explain("executionStats")
"executionStats" : {
        "executionSuccess" : true,
        "nReturned" : 1,
        "executionTimeMillis" : 0,
        "totalKeysExamined" : 1
}

2、索引

  • 查看当前集合的所有索引
db.集合.getIndexes()
> db.t255.getIndexes()
[
        {
                "v" : 2,
                "key" : {
                        "_id" : 1
                }
                "name" : "_id_"
                "ns" : "test.t255"
        },
        {
                "v" : 2,
                "key" : {
                        "name" : 1
                }
                "name" : "name_1"
                "ns" : "test.t255"
        }
]
  • 删除索引
db.集合.dropIndex({'索引名称' : 1})
> db.t255.dropIndex({name : 1})
{ "nIndexesWas" : 2, "ok" : 1}
> db.t255.getIndexes()
[
        {
                "v" : 2,
                "key" : {
                        "_id" : 1
                }
                "name" : "_id_"
                "ns" : "test.t255"
        }
]
  • 创建唯一索引(索引的值是唯一的)
db.集合.ensureIndex({"索引名称" : 1}, {"unique" : true})

七、mongodb与python交互

1、实例化与插入

2、插入和更新

3、删除

标签：总结,name,ObjectId,MongoDB,age,db,学习,gender,id
From： https://blog.csdn.net/weixin_44926447/article/details/136628248

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