mongo

Posted 2021-11-25 dadddd

mongo中n对n的关联关系的基本操作

学生表

db.students.remove({})
db.students.insert({_id:"1",name : "a"})
db.students.insert({_id:"2",name : "b"})
db.students.insert({_id:"3",name : "c"})

 

课程表

db.class.remove({})
db.class.insert({_id:"4",classname:"english"})
db.class.insert({_id:"5",classname:"math"})
db.class.insert({_id:"6",classname:"chinese"})

 

学生选课表：两种表现形式

db.choose.remove({})
db.choose.insert({_id:"1",name:"a",class:[{_id:"5",classname:"math"},{_id:"6",classname:"chinese"}]})
db.choose.insert({_id:"1",name:"a",class:[{_id:"4",classname:"english"},{_id:"6",classname:"chinese"}]})
db.choose.insert({_id:"1",name:"a",class:[{_id:"4",classname:"english"},{_id:"5",classname:"math"}]})

 

db.choose.remove({})
db.choose.insert({_id:"1",name:"a",class:["5","6"]})
db.choose.insert({_id:"1",name:"a",class:["4","6"]})
db.choose.insert({_id:"1",name:"a",class:["4","5"]})

 

1. 查看a同学所选的课程

db.choose.find({_id:"1"},{class: 1._id: 0})

 

2.查看english课有哪些同学选

db.choose.find(
{class: {$eleMatch: {classname: "english"}}},
{_id,1}
)

 

db.choose.find({class:"5"},{_id:1,name:1})

 

3.删除a同学

db.choose.remove({name:"a"})

 

4.删除english课

db.choose.update({},{"$pull":{class:{classname:"english"}}}, {multi: true})

db.choose.update({},{"$pull":{class:"4"}},{multi:true})

 

5.a同学增加english

db.choose.update({name:"a"},{"$push":{class:{_id:"4",classname:"english"}}})

db.choose.update({name:"a"},{"$push":{class:"4"}})