mogodbshell中数组对象查询修改方法

在mongodb中，存在如下数据

{ "_id" : ObjectId("59af55078a8fc5e51ff425de"), "title" : "title1", "col" : "col
1", "reader" : [ { "readername" : "jim", "isread" : true }, { "readername" : "ka
te" }, { "readername" : "lilei" } ], "begindate" : "Wed Sep 06 2017 09:53:11 GMT
+0800 (中国标准时间)" }
{ "_id" : ObjectId("59af552e8a8fc5e51ff425df"), "title" : "title2", "col" : "col
1", "reader" : [ { "readername" : "jim" }, { "readername" : "kate" }, { "readern
ame" : "lilei" }, { "readername" : "lily" } ], "begindate" : "Wed Sep 06 2017 09
:53:50 GMT+0800 (中国标准时间)" }
{ "_id" : ObjectId("59af55458a8fc5e51ff425e0"), "title" : "title3", "col" : "col
1", "reader" : [ { "readername" : "jim" }, { "readername" : "kate" } ], "beginda
te" : "Wed Sep 06 2017 09:54:13 GMT+0800 (中国标准时间)" }

需求1：查询栏目是col1，且读者是lily的记录：

> db.articles.find({col:'col1','reader.readername':'lily'})
//查询结果
{ "_id" : ObjectId("59af552e8a8fc5e51ff425df"), "title" : "title2", "col" : "col
1", "reader" : [ { "readername" : "jim" }, { "readername" : "kate" }, { "readern
ame" : "lilei" }, { "readername" : "lily" } ], "begindate" : "Wed Sep 06 2017 09
:53:50 GMT+0800 (中国标准时间)" }

即数组中的对象用形如“数组名.字段”组成

需求2：把标题为title2，且读者为lily的已读记录‘isread’设置为true

> db.articles.update({title:'title2','reader.readername':'lily'},{$set:{'reader.
$.isread':true}})

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

{ "_id" : ObjectId("59af552e8a8fc5e51ff425df"), "title" : "title2", "col" : "col
1", "reader" : [ { "readername" : "jim" }, { "readername" : "kate" }, { "readern
ame" : "lilei" }, { "readername" : "lily", "isread" : true } ], "begindate" : "W
ed Sep 06 2017 09:53:50 GMT+0800 (中国标准时间)" }

核心是$，可以理解为数组定位器

需求3：删除名为title2下的reader名字为lilei的读者对象：

//未删除前数据
{ "_id" : ObjectId("59af552e8a8fc5e51ff425df"), "title" : "title2", "col" : "col
1", "reader" : [ { "readername" : "jim" }, { "readername" : "kate" }, { "readern
ame" : "lilei" }, { "readername" : "lily", "isread" : true } ], "begindate" : "W
ed Sep 06 2017 09:53:50 GMT+0800 (中国标准时间)" }

//执行命令
> db.articles.update({title:'title2','reader.readername':'lilei'},{$pull:{'reader':{readername:'lilei'}}})

//执行命令后查询的结果
> db.articles.find({title:'title2'});
{ "_id" : ObjectId("59af552e8a8fc5e51ff425df"), "title" : "title2", "col" : "col
1", "reader" : [ { "readername" : "jim" }, { "readername" : "kate" }, { "readern
ame" : "lily", "isread" : true } ], "begindate" : "Wed Sep 06 2017 09:53:50 GMT+
0800 (中国标准时间)" }

核心是用$pull命令查找数组名称，然后通过属性值删除数组内的对象记录