MongoDB更新文档

本文命令都是在mongo shell下实战的，到了真实的web项目中这些命令对应的实现都是有封装的，所以不用被吓到

先贴上官方正统文档 英文文档,下面的链接都是中文社区的 😂

MongoDB更新文档的方法很多，尤其是在3.2以后，主要的方法有以下几种.

db.collection.updateOne() 即使可能有多个文档通过过滤条件匹配到，但是也最多也只更新一个文档。3.2 新版功能.

db.collection.updateMany() 更新所有通过过滤条件匹配到的文档.3.2 新版功能.

db.collection.replaceOne() 即使可能有多个文档通过过滤条件匹配到，但是也最多也只替换一个文档。3.2 新版功能.

db.collection.update() 即使可能有多个文档通过过滤条件匹配到，但是也最多也只更新或者替换一个文档。默认情况下只更新 一个 文档。要更新多个文档，请使用 multi 选项

db.collection.save() 通过传入的文档来替换已有文档。

本文只对update()方法做说明，其余几个放发内置了链接可以去看官方文档

update()语法

db.collection.update(
   <filter>,
   <update>,
   {
     upsert: <boolean>,
     writeConcern: <document>,
     collation: <document>
   }
)

参数说明：

• query : update的查询条件，类似sql update查询内where条件。
• update : update的对象和一些更新的操作符（如$set,$inc...）等，也可以理解为sql update查询内set后面的
• upsert : 可选，这个参数的意思是，如果不存在update的记录，是否插入一条新的文档,true为插入，默认是false，不插入。
• multi : 可选，mongodb 默认是false,只更新找到的第一条记录，如果这个参数为true,就把按条件查出来多条记录全部更新。
• writeConcern :可选，抛出异常的级别。

update过滤文档语法

1.相等查询

{ <field1>: <value1>, <field2>: <value2>...}

表达式指定相等条件,查询满足 <field> 等于 <value>的所有文档，可以指定多组条件

2.查询操作符来指定查询条件

{ <field1>: { <operator1>: <value1> }, ... }

指定操作符查询条件需要嵌套{},如查询age字段大于20的

{"age" : {$gt: 20}}

我们接着上一篇文章来测试，首先查看users文档的记录

> db.users.find().pretty()
{
    "_id" : ObjectId("5c77461437955b945af7321f"),
    "name" : "缘来是你",
    "age" : 27,
    "gender" : "male"
}
{
    "_id" : ObjectId("5c77499137955b945af73220"),
    "name" : "tom",
    "age" : 22,
    "gender" : "male"
}
{
    "_id" : ObjectId("5c77499137955b945af73221"),
    "name" : "Linda",
    "age" : 18,
    "gender" : "female"
}
{
    "_id" : ObjectId("5c77731d37955b945af73222"),
    "name" : "Hanmeimei",
    "age" : 17,
    "gender" : "female"
}
{
    "_id" : ObjectId("5c7774b736397a1c0aa425ea"),
    "name" : "Jack",
    "age" : 42,
    "gender" : "male"
}
{
    "_id" : ObjectId("5c7774b736397a1c0aa425eb"),
    "name" : "Lucy",
    "age" : 23,
    "gender" : "female"
}

pretty()方法可以在终端美化输出结果

我们将tom的age改为20

> db.users.update({"name" : "tom"}, {$set : {"age" : 20}})
WriteResult({ "nMatched" : 1, "nUpserted" : 0, "nModified" : 1 })
> db.users.find()
{ "_id" : ObjectId("5c77461437955b945af7321f"), "name" : "缘来是你", "age" : 27, "gender" : "male" }
{ "_id" : ObjectId("5c77499137955b945af73220"), "name" : "tom", "age" : 20, "gender" : "male" }
{ "_id" : ObjectId("5c77499137955b945af73221"), "name" : "Linda", "age" : 18, "gender" : "female" }
{ "_id" : ObjectId("5c77731d37955b945af73222"), "name" : "Hanmeimei", "age" : 17, "gender" : "female" }
{ "_id" : ObjectId("5c7774b736397a1c0aa425ea"), "name" : "Jack", "age" : 42, "gender" : "male" }
{ "_id" : ObjectId("5c7774b736397a1c0aa425eb"), "name" : "Lucy", "age" : 23, "gender" : "female" }

这里就不用pretty()方法美化了，篇幅太长😂

看第二条文档，tom的年龄被改为了20

将Jack和Lucy的年龄改为25该怎么做呢，先来个错误命令

> db.users.update({"name" : {$in : ["Jack", "Lucy"]}}, {$set: {"age" : 25}})
WriteResult({ "nMatched" : 1, "nUpserted" : 0, "nModified" : 1 })
> db.users.find()
{ "_id" : ObjectId("5c77461437955b945af7321f"), "name" : "缘来是你", "age" : 27, "gender" : "male" }
{ "_id" : ObjectId("5c77499137955b945af73220"), "name" : "tom", "age" : 20, "gender" : "male" }
{ "_id" : ObjectId("5c77499137955b945af73221"), "name" : "Linda", "age" : 18, "gender" : "female" }
{ "_id" : ObjectId("5c77731d37955b945af73222"), "name" : "Hanmeimei", "age" : 17, "gender" : "female" }
{ "_id" : ObjectId("5c7774b736397a1c0aa425ea"), "name" : "Jack", "age" : 25, "gender" : "male" }
{ "_id" : ObjectId("5c7774b736397a1c0aa425eb"), "name" : "Lucy", "age" : 23, "gender" : "female" }

问题:只有Jack的年龄被更新为25而Lucy的没有，前面说了update()只更新匹配到的第一条记录，要想更新多条需要设置multi参数。来看下一条命令

> db.users.update({"name" : {$in : ["Jack", "Lucy"]}}, {$set: {"age" : 28}}, {multi : true})
WriteResult({ "nMatched" : 2, "nUpserted" : 0, "nModified" : 2 })
> db.users.find()
{ "_id" : ObjectId("5c77461437955b945af7321f"), "name" : "缘来是你", "age" : 27, "gender" : "male" }
{ "_id" : ObjectId("5c77499137955b945af73220"), "name" : "tom", "age" : 20, "gender" : "male" }
{ "_id" : ObjectId("5c77499137955b945af73221"), "name" : "Linda", "age" : 18, "gender" : "female" }
{ "_id" : ObjectId("5c77731d37955b945af73222"), "name" : "Hanmeimei", "age" : 17, "gender" : "female" }
{ "_id" : ObjectId("5c7774b736397a1c0aa425ea"), "name" : "Jack", "age" : 28, "gender" : "male" }
{ "_id" : ObjectId("5c7774b736397a1c0aa425eb"), "name" : "Lucy", "age" : 28, "gender" : "female" }

这里加了{multi: true}参数，所以Jack和Lucy的age都被设置成了28。如果更新的文档不存在呢？我们尝试一下将upsert设置为true，来看下一条命令

> db.users.update({"name":"Lucys"}, {$set : {"is_active": 0}}, {upsert: true})
WriteResult({
    "nMatched" : 0,
    "nUpserted" : 1,
    "nModified" : 0,
    "_id" : ObjectId("5c77946b96c95d22dfe8b411")
})
> db.users.find()
{ "_id" : ObjectId("5c77461437955b945af7321f"), "name" : "缘来是你", "age" : 27, "gender" : "male" }
{ "_id" : ObjectId("5c77499137955b945af73220"), "name" : "tom", "age" : 20, "gender" : "male" }
{ "_id" : ObjectId("5c77499137955b945af73221"), "name" : "Linda", "age" : 18, "gender" : "female" }
{ "_id" : ObjectId("5c77731d37955b945af73222"), "name" : "Hanmeimei", "age" : 17, "gender" : "female" }
{ "_id" : ObjectId("5c7774b736397a1c0aa425ea"), "name" : "Jack", "age" : 28, "gender" : "male" }
{ "_id" : ObjectId("5c7774b736397a1c0aa425eb"), "name" : "Lucy", "age" : 28, "gender" : "female" }
{ "_id" : ObjectId("5c77946b96c95d22dfe8b411"), "name" : "Lucys", "is_active" : 0 }

可以看到这里mongodb新增了一条文档，而且除了_id字段外，其余的字段都出现在了更新语句中，没出现的在文档中没有.对于upsert和multi参数你也可以这么设置

> db.users.update({"age": {$gt: 25}}, {$set: {"is_active": 1}}, false, true)
WriteResult({ "nMatched" : 3, "nUpserted" : 0, "nModified" : 3 })
> db.users.find()
{ "_id" : ObjectId("5c77461437955b945af7321f"), "name" : "缘来是你", "age" : 27, "gender" : "male", "is_active" : 1 }
{ "_id" : ObjectId("5c77499137955b945af73220"), "name" : "tom", "age" : 20, "gender" : "male" }
{ "_id" : ObjectId("5c77499137955b945af73221"), "name" : "Linda", "age" : 18, "gender" : "female" }
{ "_id" : ObjectId("5c77731d37955b945af73222"), "name" : "Hanmeimei", "age" : 17, "gender" : "female" }
{ "_id" : ObjectId("5c7774b736397a1c0aa425ea"), "name" : "Jack", "age" : 28, "gender" : "male", "is_active" : 1 }
{ "_id" : ObjectId("5c7774b736397a1c0aa425eb"), "name" : "Lucy", "age" : 28, "gender" : "female", "is_active" : 1 }
{ "_id" : ObjectId("5c77946b96c95d22dfe8b411"), "name" : "Lucys", "is_active" : 0 }

第一个参数false是upsert的值，第二个true是multi的值