MongoDB 增删改查操作

1、添加文档
db.集合名.insert({k1:v1,k2:v2...}) ：向当前数据库的该集合下添加文档

我们在添加文档的时候有如下注意点：

a) 文档就是键值对，数据类型是 BSON 格式，支持的值更加丰富。 BSON 是 JSON 的扩展，新增了诸如日期，浮点等 JSON 不支持的数据类型。

b) 在添加的文档里面，都有一个 '_id' 的键，值为对象类型 ObjectID ，在这里，我们解释下 ObjectID 类型：

每个文档都有一个 _id 字段，并且同一集合中的 _id 值唯一，该字段可以是任意类型的数据，默认是一个 ObjectID 对象。 ObjectID 对象数据组成：时间戳|机器码|PID|计数器 _id 的键值我们可以自己输入，但是不能重复，但要注意的一点是在插入数据的时候，如果 _id 的值重复则会报错

c) 可以使用 js 代码来完成批量插入文档

example：

for(var i=1;i<=10;i++){
... db.php.insert({'name':'xiaobai'+i,'age':i,'email':'xiaobai'+i+'@gmail.com'})
... }
WriteResult({ "nInserted" : 1 })
db.php.find()
{ "_id" : ObjectId("5b931b74a39e4f4842ba36b3"), "name" : "xiaoming", "age" : 20, "email" : "[email protected]" }
{ "_id" : ObjectId("5b931b7ca39e4f4842ba36b4"), "name" : "xiaohong", "age" : 18, "email" : "[email protected]" }
{ "_id" : ObjectId("5b931dfba39e4f4842ba36b5"), "name" : "xiaobai1", "age" : 1, "email" : "[email protected]" }
{ "_id" : ObjectId("5b931dfba39e4f4842ba36b6"), "name" : "xiaobai2", "age" : 2, "email" : "[email protected]" }
{ "_id" : ObjectId("5b931dfba39e4f4842ba36b7"), "name" : "xiaobai3", "age" : 3, "email" : "[email protected]" }
{ "_id" : ObjectId("5b931dfba39e4f4842ba36b8"), "name" : "xiaobai4", "age" : 4, "email" : "[email protected]" }
{ "_id" : ObjectId("5b931dfba39e4f4842ba36b9"), "name" : "xiaobai5", "age" : 5, "email" : "[email protected]" }
{ "_id" : ObjectId("5b931dfba39e4f4842ba36ba"), "name" : "xiaobai6", "age" : 6, "email" : "[email protected]" }
{ "_id" : ObjectId("5b931dfba39e4f4842ba36bb"), "name" : "xiaobai7", "age" : 7, "email" : "[email protected]" }
{ "_id" : ObjectId("5b931dfba39e4f4842ba36bc"), "name" : "xiaobai8", "age" : 8, "email" : "[email protected]" }
{ "_id" : ObjectId("5b931dfba39e4f4842ba36bd"), "name" : "xiaobai9", "age" : 9, "email" : "[email protected]" }
{ "_id" : ObjectId("5b931dfba39e4f4842ba36be"), "name" : "xiaobai10", "age" : 10, "email" : "[email protected]" }
2、删除文档
db.集合名.remove{(条件)} ：删除当前数据库下指定集合中满足条件的文档(不写条件则删除所有的文档)

example：

db.php.remove({age:20})
WriteResult({ "nRemoved" : 1 })
db.php.remove({age:{'$lt':6}})
WriteResult({ "nRemoved" : 5 })
db.php.find()
{ "_id" : ObjectId("5b931b7ca39e4f4842ba36b4"), "name" : "xiaohong", "age" : 18, "email" : "[email protected]" }
{ "_id" : ObjectId("5b931dfba39e4f4842ba36ba"), "name" : "xiaobai6", "age" : 6, "email" : "[email protected]" }
{ "_id" : ObjectId("5b931dfba39e4f4842ba36bb"), "name" : "xiaobai7", "age" : 7, "email" : "[email protected]" }
{ "_id" : ObjectId("5b931dfba39e4f4842ba36bc"), "name" : "xiaobai8", "age" : 8, "email" : "[email protected]" }
{ "_id" : ObjectId("5b931dfba39e4f4842ba36bd"), "name" : "xiaobai9", "age" : 9, "email" : "[email protected]" }
{ "_id" : ObjectId("5b931dfba39e4f4842ba36be"), "name" : "xiaobai10", "age" : 10, "email" : "[email protected]" }
这里我们在删除 php 集合中年龄小于6的文档时，我们使用了操作符来完成。

比较运算符

操作符效果lt小于lte小于等于in包含nin不包含

逻辑运算符

操作符效果or或者not不存在where位置

特别的 $exists: true 表示字段存在
排序 sort

操作效果desc降序

3、更新文档
更新文档有两种方式进行修改

方法一、直接修改

db.集合名.update({条件},{新的文档}) ：修改当前数据库下指定集合中满足条件的文档信息

example：

db.php.find()
{ "_id" : ObjectId("5b931b7ca39e4f4842ba36b4"), "name" : "xiaohong", "age" : 18, "email" : "[email protected]" }
db.php.update({age:18},{name:'xiaobai5'})
WriteResult({ "nMatched" : 1, "nUpserted" : 0, "nModified" : 1 })
db.php.find()
{ "_id" : ObjectId("5b931b7ca39e4f4842ba36b4"), "name" : "xiaobai5" }
db.集合.update(条件,新文档,是否新增,是否修改多条) ：修改当前数据库下指定集合中满足条件的文档信息

是否新增：如果值是1(true)则没有满足条件的 则添加
是否修改多条：若值是1(true)，如果满足条件的有多个文档 则都要修改
example：

db.php.update({age:10},{name:'xiaoli'},true,true)
WriteResult({
"nMatched" : 0,
"nUpserted" : 0,
"nModified" : 0,
"writeError" : {
"code" : 9,
"errmsg" : "multi update only works with $ operators"
}
})
方法二、使用修改器

example：

我们要修改 age=6 的文档名称为 xiaosan ，并且其他键值不能丢失

我们可以使用修改器

set ：修改某一个字段，如果该字段不存在就增这个字段
语法：db.集合名.update({条件},{修改器名称:{修改的键:修改的新值}})

db.php.update({age:6},{'$set':{name:'xiaosan'}})
WriteResult({ "nMatched" : 1, "nUpserted" : 0, "nModified" : 1 })
那如果我们要修改 age=10 的文档的年龄增加十岁，我们可以这样做：

db.php.update({age:10},{$inc:{age:10}})
WriteResult({ "nMatched" : 1, "nUpserted" : 0, "nModified" : 1 })
4、查询文档
语法： db.集合名.find({条件})

example：

取出 php 集合里面的第一个文档

db.php.findOne()
{ "_id" : ObjectId("5b931b7ca39e4f4842ba36b4"), "name" : "xiaobai5" }
取出 php 集合里面 age=6 的文档

db.php.find({age:6})
{ "_id" : ObjectId("5b931dfba39e4f4842ba36ba"), "name" : "xiaosan", "age" : 6, "email" : "[email protected]" }
取出 php 集合里面 age>8 的文档

db.php.find({age:{'$gt':8}})
{ "_id" : ObjectId("5b931dfba39e4f4842ba36bd"), "name" : "xiaobai9", "age" : 9, "email" : "[email protected]" }
{ "_id" : ObjectId("5b931dfba39e4f4842ba36be"), "name" : "xiaobai10", "age" : 20, "email" : "[email protected]" }
取出 php 集合里面的文档，只显示 name 键

db.php.find({},{age:1})//1表示只显示age键值
{ "_id" : ObjectId("5b931b7ca39e4f4842ba36b4") }
{ "_id" : ObjectId("5b931dfba39e4f4842ba36ba"), "age" : 6 }
{ "_id" : ObjectId("5b931dfba39e4f4842ba36bb"), "age" : 7 }
{ "_id" : ObjectId("5b931dfba39e4f4842ba36bc"), "age" : 8 }
{ "_id" : ObjectId("5b931dfba39e4f4842ba36bd"), "age" : 9 }
{ "_id" : ObjectId("5b931dfba39e4f4842ba36be"), "age" : 20 }
db.php.find({},{age:0})//1表示除了显示age键值，其他的都显示
{ "_id" : ObjectId("5b931b7ca39e4f4842ba36b4"), "name" : "xiaobai5" }
{ "_id" : ObjectId("5b931dfba39e4f4842ba36ba"), "name" : "xiaosan", "email" : "[email protected]" }
{ "_id" : ObjectId("5b931dfba39e4f4842ba36bb"), "name" : "xiaobai7", "email" : "[email protected]" }
{ "_id" : ObjectId("5b931dfba39e4f4842ba36bc"), "name" : "xiaobai8", "email" : "[email protected]" }
{ "_id" : ObjectId("5b931dfba39e4f4842ba36bd"), "name" : "xiaobai9", "email" : "[email protected]" }
{ "_id" : ObjectId("5b931dfba39e4f4842ba36be"), "name" : "xiaobai10", "email" : "[email protected]" }
根据年龄的(降序|升序)来显示文档

db.集合名.find().sort({age:1})根据年龄升序
db.集合名.find().sort({age:0})根据年龄降序
显示 php 集合中的前三个文档

db.php.find().limit(3)
{ "_id" : ObjectId("5b931b7ca39e4f4842ba36b4"), "name" : "xiaobai5" }
{ "_id" : ObjectId("5b931dfba39e4f4842ba36ba"), "name" : "xiaosan", "age" : 6, "email" : "[email protected]" }
{ "_id" : ObjectId("5b931dfba39e4f4842ba36bb"), "name" : "xiaobai7", "age" : 7, "email" : "[email protected]" }
显示 php 集合中的第三个文档到第五个文档

db.php.find().skip(2).limit(3)
{ "_id" : ObjectId("5b931dfba39e4f4842ba36bb"), "name" : "xiaobai7", "age" : 7, "email" : "[email protected]" }
{ "_id" : ObjectId("5b931dfba39e4f4842ba36bc"), "name" : "xiaobai8", "age" : 8, "email" : "[email protected]" }
{ "_id" : ObjectId("5b931dfba39e4f4842ba36bd"), "name" : "xiaobai9", "age" : 9, "email" : "[email protected]" }
统计 php 集合中文档的个数

db.集合名.count():返回集合中有多少个文档