PatrickLiu


一、引言


         上一篇文章我们已经详细介绍了MongoDB数据库的有关查询的内容,但是这只是所有查询命令的冰山一角。所有查询命令都写完也没有必要,我只是写了一些常用的命令,对MongoDB的操作有一个基本的认识,如果大家想继续深入,可以根据自己的需要深入学习其他的命令。今天要讲一些和更新、修改有关系的语句、命令或者方法,当然不可能是所有的命令了,也只是一些常用的命令。我提供给大家一个基础,大家可以继续深入,我也会继续深入学习的。废话不多说,马上开始我们今天的写作吧。


二、MongoDB有关修改的详解

          
          我比较直接,还是直接来内容吧,有关修改的每个方法都有示例代码,应该不是很难,希望能起到抛砖引玉的作用吧。


            1、update() 方法

                    1.1、update() 方法用于更新已存在的文档。语法格式如下:

                         db.collectionName.update(
                            <query>,
                            <update>,
                            {
                              upsert: <boolean>,
                              multi: <boolean>,
                              writeConcern: <document>
                             }
                          )

                         参数说明:

                             query : update的查询条件,类似sql update查询内where后面的。

                             update : update的对象和一些更新的操作符(如$,$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objNew,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。


                    1.2、示例代码
                         
                          
                          > db.students.find({"name":"FangShiYu"})
                          { "_id" : ObjectId("5ab9de223afa6504457050e2"), "name" : "FangShiYu", "age" : 22, "sex" : 1, "school" : "ZheJiangDaXue", "address" : "GuangDongGuangZhou" }

                          //修改【name】是【FangShiYu】的【age】字段的值为【25】
                          > db.students.update({"name":"FangShiYu"},{"$set":{"age":25}})
                          WriteResult({ "nMatched" : 1, "nUpserted" : 0, "nModified" : 1 })

                          > db.students.find({"name":"FangShiYu"})
                         { "_id" : ObjectId("5ab9de223afa6504457050e2"), "name" : "FangShiYu", "age" : 25, "sex" : 1, "school" : "ZheJiangDaXue", "address" : "GuangDongGuangZhou" }
>



            2、$set 修改器:针对指定字段设置指定的值,修改字段的值


                   语法:db.collectionName.update({query},{"$set":{<key>:<value>}})

                   参数说明:

                          query:查询条件

                          key:要操作的字段名

                          value:要给key字段赋的值


                     在MongoDB数据库中通过 $set 修改器和 update()方法配合使用,起到修改指定字段的作用。


                     2.1、示例代码:

                          > db.students.find({"name":"FangShiYu"})
                          { "_id" : ObjectId("5ab9de223afa6504457050e2"), "name" : "FangShiYu", "age" : 22, "sex" : 1, "school" : "ZheJiangDaXue", "address" : "GuangDongGuangZhou" }

                          //修改【name】是【FangShiYu】的【age】字段的值为【25】
                          > db.students.update({"name":"FangShiYu"},{"$set":{"age":25}})
                          WriteResult({ "nMatched" : 1, "nUpserted" : 0, "nModified" : 1 })

                          > db.students.find({"name":"FangShiYu"})
                         { "_id" : ObjectId("5ab9de223afa6504457050e2"), "name" : "FangShiYu", "age" : 25, "sex" : 1, "school" : "ZheJiangDaXue", "address" : "GuangDongGuangZhou" }
                          >




            2、$inc 修改器:在数值字段在原有的基础上再增加指定的数值,其值可以是正数,也可以是负数,负数是减多少


                   语法:db.collectionName.update({query},{"$inc":{<key>:number}})

                   参数说明:

                          query:查询条件

                          key:要操作的字段名

                          number:增加的数量,可以是正数也可以是负数,正数相加,负数相减


                     在MongoDB数据库中通过 $inc 修改器和 update()方法配合使用,起到让数值字段在原有的基础上增加指定的数值的作用。                     



                     2.1、示例代码:【age】字段在原有基础上加 【正数:1】


                         > db.students.find({"name":"FangShiYu"})
                         { "_id" : ObjectId("5ab9de223afa6504457050e2"), "name" : "FangShiYu", "age" : 25, "sex" : 1, "school" : "ZheJiangDaXue", "address" : "GuangDongGuangZhou" }

                         //修改【name】是【FangShiYu】的【age】字段的值,让其值增加1,最受值为【26】
                         > db.students.update({"name":"FangShiYu"},{"$inc":{"age":1}})
                         WriteResult({ "nMatched" : 1, "nUpserted" : 0, "nModified" : 1 })

                         > db.students.find({"name":"FangShiYu"})
                        { "_id" : ObjectId("5ab9de223afa6504457050e2"), "name" : "FangShiYu", "age" : 26, "sex" : 1, "school" : "ZheJiangDaXue", "address" : "GuangDongGuangZhou" }
                         >


                     2.2、示例代码:【age】字段在原有基础上加 【负数:-5】


                         > db.students.find({"name":"FangShiYu"})
                         { "_id" : ObjectId("5ab9de223afa6504457050e2"), "name" : "FangShiYu", "age" : 26, "sex" : 1, "school" : "ZheJiangDaXue", "address" : "GuangDongGuangZhou" }


                         > db.students.update({"name":"FangShiYu"},{"$inc":{"age":-5}})
                         WriteResult({ "nMatched" : 1, "nUpserted" : 0, "nModified" : 1 })

                         > db.students.find({"name":"FangShiYu"})
                         { "_id" : ObjectId("5ab9de223afa6504457050e2"), "name" : "FangShiYu", "age" : 21, "sex" : 1, "school" : "ZheJiangDaXue", "address" : "GuangDongGuangZhou" }
                         >




            3、$push 修改器:针对指定的字段插入文档列表,如果该字段不存在,会建立该字段并插入内文档容,如果存在,就向该字段的列表里追加文档内容。例如:留言板

                   documents={document}

                   语法:db.collectionName.update({query},{"$push":{<key>:document}})

                   参数说明:

                          query:查询条件

                          document:一个文档对象

                          key:要操作的字段名


                     在MongoDB数据库中通过 $push 修改器和 update()方法配合使用,起到留言板的效果,比如:多个人可以给某一个女生留言,每条留言就是一个文档,多个文档组成列表



                     2.1、示例代码:【messages】集合中原来没有【comments】字段


                         //原始记录
                         > db.messages.find()
                        { "_id" : ObjectId("5abdc29b678c8239350e8a20"), "name" : "peny", "age" : 22, "sex" : 0 }

                        > query={"name":"tom","say":"i love u!"}
                        { "name" : "tom", "say" : "i love u!" }

                        > db.messages.update({"name":"peny"},{"$push":{"comments":query}})
                        WriteResult({ "nMatched" : 1, "nUpserted" : 0, "nModified" : 1 })

                        //网【messages】集合中增加了【comments】字段,并增加了一个列表,也可以说数组
                        > db.messages.find()
                        { "_id" : ObjectId("5abdc29b678c8239350e8a20"), "name" : "peny", "age" : 22, "sex" : 0, "comments" : [ { "name" : "tom", "say" : "i love u!" } ] }
                        >



                     2.2、示例代码:在【messages】集合基础上继续向【comments】字段追加文档内容


                         //原始记录
                         > db.messages.find()
                         { "_id" : ObjectId("5abdc29b678c8239350e8a20"), "name" : "peny", "age" : 22, "sex" : 0, "comments" : [ { "name" : "tom", "say" : "i love u!" } ] }

                         > query={"name":"jim","say":"i want to know you!"}
                         { "name" : "jim", "say" : "i want to know you!" }

                         > db.messages.update({"name":"peny"},{"$push":{"comments":query}})
                         WriteResult({ "nMatched" : 1, "nUpserted" : 0, "nModified" : 1 })

                         > db.messages.find()
                         { "_id" : ObjectId("5abdc29b678c8239350e8a20"), "name" : "peny", "age" : 22, "sex" : 0, "comments" : [ { "name" : "tom", "say" : "i love u!" }, { "name" : "jim", "say" : "i want to know you!" } ] }
                         >




             4、$each 修改器: $each 修改器、$push 修改器必须组合使用,可以一次增加由多个文档组成的列表,字段有,就追加文档,没有就创建该字段并增加一个由多个文档组成的列表数据


                   documents=[{document1},{document2},{document3}....{documentn}]

                   语法:db.collectionName.update({query},{"$push":{<key>:{"$each":documents}}})

                   参数说明:

                          query:查询条件

                          documents:文档列表,也可以称文档数组

                          key:要操作的字段名


                     在MongoDB数据库中通过 $each 修改器、$push 修改器 和 update()方法配合使用,起到的作用类似一次插入由多个文档组成的列表。



                     2.1、示例代码:【messages】集合中原来没有【comments】字段


                         //原始记录
                         > db.messages.find()
                         { "_id" : ObjectId("5abdc844678c8239350e8a21"), "name" : "peny", "age" : 22, "sex" : 0 }


                         >query=[{"name":"tom","say":"hello!"},{"name":"jackey","say":"i love u!"},{"name":"jerry","say":"i want u"}];

                         [
                                  {
                                         "name" : "tom",
                                         "say" : "hello!"
                                  },
                                 {
                                         "name" : "jackey",
                                         "say" : "i love u!"
                                  },
                                  {
                                         "name" : "jerry",
                                         "say" : "i want u"
                                   }
                          ]


                        > db.messages.update({"name":"peny"},{"$push":{"comments":{"$each":query}}})
                        WriteResult({ "nMatched" : 1, "nUpserted" : 0, "nModified" : 1 })

                        > db.messages.find()
                        { "_id" : ObjectId("5abdc844678c8239350e8a21"), "name" : "peny", "age" : 22, "sex" : 0, "comments" : [ { "name" : "tom", "say" : "hello!" }, { "name" : "jackey", "say" : "i love u!" }, { "name" : "jerry", "say" : "i want u" } ] }
                        >




                     2.2、示例代码:在【messages】集合基础上继续向【comments】字段追加文档内容


                         //原始记录
                         > db.messages.find()
                         { "_id" : ObjectId("5abdc844678c8239350e8a21"), "name" : "peny", "age" : 22, "sex" : 0, "comments" : [ { "name" : "tom", "say" : "hello!" }, { "name" : "jackey", "say" : "i love u!" }, { "name" : "jerry", "say" : "i want u" } ] }


                         > query=[{"name":"jason","say":"i know you!"},{"name":"bob","say":"i miss you!"}];
                         [
                                  {
                                          "name" : "jason",
                                          "say" : "i know you!"
                                  },
                                 {
                                          "name" : "bob",
                                          "say" : "i miss you!"
                                  }
                          ]


                         > db.messages.update({"name":"peny"},{"$push":{"comments":{"$each":query}}})
                         WriteResult({ "nMatched" : 1, "nUpserted" : 0, "nModified" : 1 })

                         //追加了文档数据
                         > db.messages.find()
                         { "_id" : ObjectId("5abdc844678c8239350e8a21"), "name" : "peny", "age" : 22, "sex" : 0, "comments" : [ { "name" : "tom", "say" : "hello!" }, { "name" : "jackey", "say" : "i love u!" }, { "name" : "jerry", "say" : "i want u" }, { "name" : "jason", "say" : "i know you!" }, { "name" : "bob", "say" : "i miss you!" } ] }
                         >


                    

             5、$slice 修改器:控制记录保存的条数,如果以前有多条会把以前的清空保存条件所规定的记录,如果操作的字段不存在,就会创建该字段


                   documents=[{document1},{document2},{document3}....{documentn}]

                   语法:db.collectionName.update({query},{$push:{<key>:{$each:documents,$slice:number}}})

                   参数说明:

                          query:查询条件

                          documents:文档列表,也可以称文档数组

                          key:要操作的字段名

                          number:控制显示的数量,正数保留最早的number条记录,负数保留最新的number条记录



                     2.1、示例代码:【messages】集合中原来没有【comments】字段


                         //原始记录
                         > db.messages.find()
                         { "_id" : ObjectId("5abdceca678c8239350e8a22"), "name" : "peny", "age" : 18, "sex" : 0 }


                         > var query=[{"name":"lilei","say":"hello"},{"name":"hanmeimei","say":"i miss u"},{"name":"tom","say":"i watch u"},{"monster":"ghost","say":"i want u"}];

                         //保存最早的两条记录,也就是【name】分别是:lilei和hanmeimei
                         > db.messages.update({"name":"peny"},{$push:{"comments":{$each:query,$slice:2}}})

                         WriteResult({ "nMatched" : 1, "nUpserted" : 0, "nModified" : 1 })


                         > db.messages.find()
                         { "_id" : ObjectId("5abdceca678c8239350e8a22"), "name" : "peny", "age" : 18, "sex" : 0, "comments" : [ { "name" : "lilei", "say" : "hello" }, { "name" : "hanmeimei", "say" : "i miss u" } ] }
                         >




                     2.2、示例代码:在【messages】集合基础上向【comments】字段文档内容


                         //原始记录
                         > db.messages.find()
                         { "_id" : ObjectId("5abdceca678c8239350e8a22"), "name" : "peny", "age" : 18, "sex" : 0, "comments" : [ { "name" : "lilei", "say" : "hello" }, { "name" : "hanmeimei", "say" : "i miss u" } ] }

                          > var query=[{"name":"tom","say":"i watch u"},{"monster":"ghost","say":"i want u"}];

                          //只会保留最新的记录,也就是【name】的值是:monster的文档
                          > db.messages.update({"name":"peny"},{$push:{"comments":{$each:query,$slice:1}}})
                          WriteResult({ "nMatched" : 1, "nUpserted" : 0, "nModified" : -1 })


                          > db.messages.find()
                         { "_id" : ObjectId("5abdceca678c8239350e8a22"), "name" : "peny", "age" : 18, "sex" : 0, "comments" : [ {"monster":"ghost","say":"i want u"}] }
                          >



             6、$addToSet 修改器:当插入一个数组时,如果数组中有重复记录,只会直插入一条,不会重复插入,会过滤掉重复的记录


                   documents=[{document1},{document2},{document3}...{documentn}]

                   语法:db.collectionName.update({query},{"$addToSet":{<key>:{"$each":documents}}})

                   
                   参数说明:

                         query:查询条件

                         documents:要插入的文档数组,也可以称作是列表,其中可以包含重复的文档

                         <key>:表示要插入数组列表的字段



                   代码实例:

                        //原始数据
                        > db.messages.find()
                       { "_id" : ObjectId("5ac5b03525eb395526dc108d"), "name" : "peny", "age" : 18, "sex" : "0" }

                        //定义要插入的文档数组,里面有重复记录,只有最后一个文档不同
                        > var documents=[{"name":"bob","say":"hi"},{"name":"bob","say":"hi"},{"name":"bob","say":"hi"},{"name":"bob","say":"hello"}];


                        //执行更新成功
                        > db.messages.update({"name":"peny"},{"$addToSet":{"comments":{"$each":documents}}});
                        WriteResult({ "nMatched" : 1, "nUpserted" : 0, "nModified" : 1 })


                        //查询结果,值插入两条记录
                        > db.messages.find()
                       { "_id" : ObjectId("5ac5b03525eb395526dc108d"), "name" : "peny", "age" : 18, "sex" : "0", "comments" : [ { "name" : "bob", "say" : "hi" }, { "name" : "bob", "say" : "hello" } ] }
                        >

 


             7、$pop修改器【删除】:从数组中进行向前删除或者向后删除,+1正数表示从尾部开始删除,-1负数表示从头开始删除。

                   语法:db.collectionName.update({query},{"$pop":{<key>:1(从后开始删除)/-1(从头开始删除)}})  

                   参数说明:

                         query:查询条件

                         <key>:表示要执行删除操作的字段名,该字段必须是数组字段

                         1(从后开始删除)/-1(从头开始删除),只能是数字1和-1,其他值非法


                   代码实例:


                        //原始数据
                        > db.messages.find()
{ "_id" : ObjectId("5ac5b03525eb395526dc108d"), "name" : "peny", "age" : 18, "sex" : "0", "comments" : [ { "name" : "bob", "say" : "hi" }, { "name" : "bob", "say" : "hello" }, { "name" : "bob", "say" : "hi1" }, { "name" : "bob", "say" : "hi2" }, { "name" : "bob", "say" : "hi3" }, { "name" : "bob", "say" : "hello5" } ] }
                       //执行删除操作,并且执行成功
                       > db.messages.update({"name":"peny"},{"$pop":{"comments":-1}})
                       WriteResult({ "nMatched" : 1, "nUpserted" : 0, "nModified" : 1 })


                       //执行结果,把comments数组的第一个元素删除了
                       > db.messages.find()
                       { "_id" : ObjectId("5ac5b03525eb395526dc108d"), "name" : "peny", "age" : 18, "sex" : "0", "comments" : [ { "name" : "bob", "say" : "hello" }, { "name" : "bob", "say" : "hi1" }, { "name" : "bob", "say" : "hi2" }, { "name" : "bob", "say" : "hi3" }, { "name" : "bob", "say" : "hello5" } ] }




             8、$pull修改器【删除】:根据指定条件删除数组字段里面的指定文档数据,pop只能删除头部或者尾部的数据


                   语法:db.collectionName.update({query},{"$pull":{<key>:{query2}}})

                   
                   参数说明:

                         query:查询条件

                         documents:要插入的文档数组,也可以称作是列表,其中可以包含重复的文档

                         <key>:表示要执行删除操作的字段名,该字段必须是数组字段

                         query2:查询数组字段中指定文档数据的查询条件
                   


                   代码实例:


                        //原始数据
                        > db.messages.find()
{ "_id" : ObjectId("5ac5b03525eb395526dc108d"), "name" : "peny", "age" : 18, "sex" : "0", "comments" : [ { "name" : "bob", "say" : "hello" }, { "name" : "bob", "say" : "hi1" }, { "name" : "bob", "say" : "hi2" }, { "name" : "bob", "say" : "hi3" }, { "name" : "bob", "say" : "hello5" } ] }


                        //执行删除操作,并且执行成功
                        > db.messages.update({"name":"peny"},{"$pull":{"comments":{"say":"hi2"}}})
                        WriteResult({ "nMatched" : 1, "nUpserted" : 0, "nModified" : 1 })


                        //结果数据,已经删除了说话内容是“hi2”的文档
                        > db.messages.find()
                        { "_id" : ObjectId("5ac5b03525eb395526dc108d"), "name" : "peny", "age" : 18, "sex" : "0", "comments" : [ { "name" : "bob", "say" : "hello" }, { "name" : "bob", "say" : "hi1" }, { "name" : "bob", "say" : "hi3" }, { "name" : "bob", "say" : "hello5" } ] }



             9、下标操作符


                   9.1、根据查询条件,确定要修改的记录,然后对数组字段中第n(索引值是n-1)个文档的指定指定字段进行值的修改


                        语法:db.collectionName.update({query},{"$set":{<key>.index.<key2>:<vlaue>}})


                        参数说明:

                              query:查询条件,确定需要修改的文档

                              $set:修改器,对某个字段进行赋值

                              <key>:表示要执行操作的字段名,该字段必须是数组字段,是*字段名

                              index:数组字段中包含多个文档,每个文档都对应这个一个具体的下标,不要过界,下标值从0开始,如:comments字段是留言板,该字段里面包含了5个文档,每个文档都是一份具体的留言内容,如果想引用数组字段中的某一个文档,可以通过下标,comments.0.say,表示comments字段里面第一份留言say的内容是什么。

                              key2:具有指定下标值的文档数据的字段名,这个字段的值将会被修改

                              value:把value表示的内容赋给key2所表示的字段


                        示例代码:


                            //原始数据
                            > db.messages.find()
                           { "_id" : ObjectId("5ac5b03525eb395526dc108d"), "name" : "peny", "age" : 18, "sex" : "0", "comments" : [ { "name" : "bob", "say" : "hello" }, { "name" : "bob", "say" : "hi1" }, { "name" : "bob", "say" : "hi3" }, { "name" : "bob", "say" : "hello5" } ] }


                            //需要修改【comments】字段里面下标为【2】的【say】字段的值,修改成功
                            > db.messages.update({"name":"peny"},{"$set":{"comments.2.say":"i am modifing!"}})
                            WriteResult({ "nMatched" : 1, "nUpserted" : 0, "nModified" : 1 })


                            //修改成功
                            > db.messages.find()
                           { "_id" : ObjectId("5ac5b03525eb395526dc108d"), "name" : "peny", "age" : 18, "sex" : "0", "comments" : [ { "name" : "bob", "say" : "hello" }, { "name" : "bob", "say" : "hi1" }, { "name" : "bob", "say" : "i am modifing!" }, { "name" : "bob", "say" : "hello5" } ] }


                            //修改【comments】字段下标是【1】的【say】字段的值
                            > db.messages.update({"name":"peny"},{"$set":{"comments.1.say":"i am modifing!"}})
                            WriteResult({ "nMatched" : 1, "nUpserted" : 0, "nModified" : 1 })


                            //修改成功
                            > db.messages.find()
                           { "_id" : ObjectId("5ac5b03525eb395526dc108d"), "name" : "peny", "age" : 18, "sex" : "0", "comments" : [ { "name" : "bob", "say" : "hello" }, { "name" : "bob", "say" : "i am modifing!" }, { "name" : "bob", "say" : "i am modifing!" }, { "name" : "bob", "say" : "hello5" } ] }



                   9.2、$ 操作符,是一个通配符,可以操作所有符合条件的记录(待测试

                        语法:db.collectionName.update({query},{"$set":{<key>.$.<key2>:<vlaue>}})

                        参数说明:

                              query:查询条件,确定需要修改的文档

                              $set:修改器,进行赋值操作

                              <key>:表示要执行操作的字段名,该字段必须是数组字段,是*字段名

                              $:是指数组字段中所有的文档,不会特指某一个文档

                              key2:具有指定下标值的文档数据的字段名,这个字段就是被修改的

                              value:把value表示的内容赋给key2所表示的字段



                        示例代码:


                             //原始数据

                             > db.students.find()
                            { "_id" : ObjectId("5ac70d2f7a05450cf60c6887"), "name" : "peny", "age" : 18, "sex" : 0, "comments" : [ { "name" : "bob", "say" : "hello" }, { "name" : "bob", "say" : "i'm changing" }, { "name" : "tom", "say" : "i love y" } ] }


                             //修改留言板里名称是【name】是【bob】的文档,把【say】字段的内容修改为【I'm a robbot】
                             > db.students.update({"comments.name":"bob"},{"$set":{"comments.$.say":"I'm robbot"}})
                             WriteResult({ "nMatched" : 1, "nUpserted" : 0, "nModified" : 1 })
                             >

                             //修改结果
                             > db.students.find()
                            { "_id" : ObjectId("5ac70d2f7a05450cf60c6887"), "name" : "peny", "age" : 18, "sex" : 0, "comments" : [ { "name" : "bob", "say" : "I'm robbot" }, { "name" : "bob", "say" : "i'm changing" }, { "name" : "tom", "say" : "i love y" } ] }




             10、upsert 状态的使用:更新操作,也可以执行插入操作


                   语法:db.collectionName.update({query},{"$set":{<key1>:<value1>,<key2>:<value2>,...<keyn>:<valuen>}},insertBoolean)

                         如果查询条件没有找到相应的文档,该表达式就会执行插入操作


                   语法:db.collectionName.update({query},{"$set":{<key1>:<value1>,<key2>:<value2>,...<keyn>:<valuen>}},insertBoolean,multiBoolean)

                         如果存在多条记录,则会修改所有的文档


                   参数说明:

                        query:查询条件,确定需要修改的文档

                        $set:修改器,用于赋值修改

                        key1-n:要操作的字段名

                        value1-n:需要给key字段赋的值,key和value一一对应。

                        insertBoolean:当记录不存在的时候是否增加记录,true表示增加,false表示不增加

                        multiBoolean:是否需要修改多条记录,true表示可以修改多条记录,false表示修改第一条记录
                        

                   示例代码:

                         //原始数据是空的,
                         > db.students.find()
                         >


                         //按通过修改增加数据
                         > db.students.update({"name":"peny"},{"$set":{"age":20,"sex":0}},true)
                         WriteResult({
                                 "nMatched" : 0,
                                 "nUpserted" : 1,
                                 "nModified" : 0,
                                 "_id" : ObjectId("5ac7187f7da6f59ef2f3836a")
                         })
                         >


                         //数据插入成功
                         > db.students.find()
                         { "_id" : ObjectId("5ac7187f7da6f59ef2f3836a"), "name" : "peny", "age" : 20, "sex" : 0 }
                         >


                         //如果数据库中存在多条名称重复的记录,为每条记录增加字段

                         //原始记录,里面有两个叫bob的文档
                         > db.students.find()
                         { "_id" : ObjectId("5ac7187f7da6f59ef2f3836a"), "name" : "peny", "age" : 20, "sex" : 0 }
                         { "_id" : ObjectId("5ac7197f7a05450cf60c6888"), "name" : "bob", "age" : 23, "sex" : 1 }
                         { "_id" : ObjectId("5ac7198b7a05450cf60c6889"), "name" : "bob", "age" : 18, "sex" : 1 }


                          //修改了两条,执行成功
                          > db.students.update({"name":"bob"},{"$set":{"school":"jiangxi"}},false,true)
                          WriteResult({ "nMatched" : 2, "nUpserted" : 0, "nModified" : 2 })



                          //查看结果,已经为两个叫bob的记录增加了一个叫school的字段。

                          > db.students.find()
                          { "_id" : ObjectId("5ac7187f7da6f59ef2f3836a"), "name" : "peny", "age" : 20, "sex" : 0 }
                          { "_id" : ObjectId("5ac7197f7a05450cf60c6888"), "name" : "bob", "age" : 23, "sex" : 1, "school" : "jiangxi" }
                          { "_id" : ObjectId("5ac7198b7a05450cf60c6889"), "name" : "bob", "age" : 18, "sex" : 1, "school" : "jiangxi" }


三、总结

       今天就写到这里了,有关更新的内容还很多,今天只是介绍一个大概的内容,让大家对MongoDB的操作有一个初步的印象。随着我们学习的深入,还会有更多的内容更新上来,不忘初衷,继续努力吧。
                                                                                     

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