The difference between a relational database and a non-relational database (i)

Talk about the difference between relational database and non-relational database the first bomb

Take the two most popular databases now: MySQL and MongoDB (a product between relational and non-relational, where we use a non-relational database for comparison with MySQL)

To give an example of a practical understanding: the system for students to choose a course (simplify to cite two of the system: students, courses)

First of all, the model built in MySQL is

Student Table (Student):

S

Sid	Name	Gender	Age	Address	Email	College	Class
1	Tom	Woman	19	A	111	Foreign language	141
2	John doe	Man	20	B	222	Management	142
3	Wang er Leper	Man	21st	C	333	Software	143

Schedule (Class):

C

Cid	Name	Teacher
1	Comprehensive Japanese	Zhao
2	Tax	Wang
3	Law	Li
4	Soft work	Sun

The intermediate table SC with c corresponding to S

TD align= "left" valign= "top" width= "188" >1

scid	sid	cid
1	1
3	2	2
5	3	4

This is the case when writing this system in MongoDB: Sid:1,name: Zhang San, gender: Female, Age:19,address:a,email:111,college: foreign language, class:141,cid:1 sid:2,name: John Doe, Gender: Male, Age:20,address:b,email:222,college: administered, class:142,cid:2 sid:3,name: Wang er Leper, gender: male, AGE:21,ADDRESS:C, Email:333,college: Software, class:143,cid:4 cid:1,name: Comprehensive Japanese, teacher: Zhao Cid:2,name: Tax law, teacher: Wang Cid:3,name: commercial law, teacher: Lee Cid                                                            : 4,name: Soft work, teacher: Sun If the student number for 1 students also selected a class number for 4 of the class, the student number 2 and selected a course number 3 of the class in MySQL inside the SC table added two fields finally this table becomes: Sc

Scid	Sid	Cid
1	1	1
2	1	4
3	2	2
4	2	3
5	3	4

And MongoDB added two document Sid:1,name: Zhang San, gender: Female, Age:19,address:a,email:111,college: foreign language, Class:141,cid:4 sid:2,name: John Doe, Gender: Male, Age:20,address:b,email:222,college: administered, Class:142,cid:3 above is on the "table" level look at the following from the perspective of the query:

The difference between a relational database and a non-relational database (i)