文档之间的关系-------------------------mongodb
Mongodb中处理文档之间的关系：
三种关系：
一对一
一对多
多对多
###一对一：
> db.wifeandhusband.insert({name:"黄蓉",husband:{name:"郭靖"}})
WriteResult({ "nInserted" : 1 })
> db.a.find().count()
20000
> db.wifeandhusband.find();
{ "_id" : ObjectId("656d8addb6da6d16e3a57044"), "name" : "黄蓉", "husband" : { "name" : "郭靖" } }
>
db.wifeandhusband.insert({name:"潘金莲",husband:{name:"武大"}})
> db.wifeandhusband.find();
{ "_id" : ObjectId("656d8addb6da6d16e3a57044"), "name" : "黄蓉", "husband" : { "name" : "郭靖" } }
{ "_id" : ObjectId("656d8b66b6da6d16e3a57045"), "name" : "潘金莲", "husband" : { "name" : "武大" } }
###一对多
###插入多条数据：一对大括号为一个数据，
> db.users.insert([{username:'aaa'},{username:'bbb'}])
BulkWriteResult({
"writeErrors" : [ ],
"writeConcernErrors" : [ ],
"nInserted" : 2,
"nUpserted" : 0,
"nMatched" : 0,
"nModified" : 0,
"nRemoved" : 0,
"upserted" : [ ]
})
> db.users.find();
{ "_id" : ObjectId("656d8cf5b6da6d16e3a57046"), "username" : "aaa" }
{ "_id" : ObjectId("656d8cf5b6da6d16e3a57047"), "username" : "bbb" }
>
##使用用户id来指明”那些订单“是哪个用户来买的，收购或者售卖的：
db.order.insert({list:["苹果","香蕉","橘子"],user_id:ObjectId("656d8cf5b6da6d16e3a57047")})
db.order.insert({list:["西瓜","香蕉"],user_id:ObjectId("656d8cf5b6da6d16e3a57047")})
db.order.insert({list:["牛肉","漫画"],user_id:ObjectId("656d8cf5b6da6d16e3a57046")})
##查找订单：
#设置用户id的变量
> var user_id = db.users.findOne({username:"aaa"})._id
> db.order.find(user_id:user_id)
SyntaxError: missing ) after argument list :
@(shell):1:21
> db.order.find({user_id:user_id})
{ "_id" : ObjectId("656d9107b6da6d16e3a5704a"), "list" : [ "牛肉", "漫画" ], "user_id" : ObjectId("656d8cf5b6da6d16e3a57046") }
再查bbb的订单有多少：
###多对多
> db.teachers.insert([{name:"洪七公"},{name:"黄药师"},{name:"龟仙人"}]);
BulkWriteResult({
"writeErrors" : [ ],
"writeConcernErrors" : [ ],
"nInserted" : 3,
"nUpserted" : 0,
"nMatched" : 0,
"nModified" : 0,
"nRemoved" : 0,
"upserted" : [ ]
})
> db.teachers.find();
{ "_id" : ObjectId("656d9420b6da6d16e3a5704c"), "name" : "洪七公" }
{ "_id" : ObjectId("656d9420b6da6d16e3a5704d"), "name" : "黄药师" }
{ "_id" : ObjectId("656d9420b6da6d16e3a5704e"), "name" : "龟仙人" }
> db.student.insert({name:"郭靖",teac_id:[ObjectId("656d9420b6da6d16e3a5704c"),ObjectId("656d9420b6da6d16e3a5704d")]});
WriteResult({ "nInserted" : 1 })
> db.student.find();
{ "_id" : ObjectId("656d96232c5120002a059cf5"), "name" : "郭靖", "teac_id" : [ ObjectId("656d9420b6da6d16e3a5704c"), ObjectId("656d9420b6da6d16e3a5704d") ] }
>
db.student.insert({name:"孙悟空",teac_id:[ObjectId("656d9420b6da6d16e3a5704e"),ObjectId("656d9420b6da6d16e3a5704d")]});
