[database] conceptual design, logical design, relational database design theory

One ： conceptual design ：
ER Model ： Entity attributes and connections
Entities and entity sets ：

Properties of entities ： Attributes and entities are nouns ：

demand –》ER chart ：

Attributes cannot be further divided , An entity can consist of multiple attributes .
Same kind of connection ：



The basic relationship between entities and derived entities ：


As shown in the figure above , Connection also has its own attributes .






Associated Nominalization ：

ER In the figure , Every entity , Must have entity identifiers , Artificially increase information for borrowing ID.

Two 、 logic design



Each entity is transformed into 1 A relationship model
1：1, stay 1 One side joins the foreign key of the other side .

Combined the primary key , And foreign keys



3、 ... and 、UML Do conceptual and logical design ：








Logic design tools ： Relational database design theory

F It's functional dependency .

Between attributes 1 Yes 1 Relationship , Is functional dependency .



Only satisfaction 1NF, Relational database












Decomposition should not compromise information and relational dependencies

attach ： View ：

Views do not store data , It's a virtual table , It's from 1 Take data from one or several tables , The view only defines data retrieval rules .