问题
I am going to make a student management system using MongoDB. I will have one table for students and another for attendance records. Can I have a key in the attendance table to reach the students table, as pictured below? How?
回答1:
The idea behind MongoDB is to eliminate (or at least minimize) relational data. Have you considered just embedding the attendance data directly into each student record? This is actually the preferred design pattern for MongoDB and can result in much better performance and scalability.
If you truly need highly relational and normalized data, you might want to reconsider using MongoDB.
回答2:
The answer depends on how you intend to use the data. You really have 2 options, embed the attendance table, or link it. More on these approaches is detailed here: http://www.mongodb.org/display/DOCS/Schema+Design
For the common use-case, you would probably embed this particular collection, so each student record would have an embedded "attendance" table. This would work because attendance records are unlikely to be shared between students, and retrieving the attendance data is likely to require the student information as well. Retrieving the attendance data would be as simple as:
db.student.find( { login : "sean" } )
{
login : "sean",
first : "Sean",
last : "Hodges",
attendance : [
{ class : "Maths", when : Date("2011-09-19T04:00:10.112Z") },
{ class : "Science", when : Date("2011-09-20T14:36:06.958Z") }
]
}
回答3:
Yes. There are no hard and fast rules. You have to look at the pros and cons of either embedding or referencing data. This video will definitely help (https://www.youtube.com/watch?v=-o_VGpJP-Q0&t=21s). In your example, the phone number attribute should be on the same table (in a document database), because the phone number of a person rarely changes.
来源：https://stackoverflow.com/questions/8129557/can-one-make-a-relational-database-using-mongodb