Database design process

Database design process

• According to the application system function , Analyze data entities （ Entity ： Stored data objects ）
  Online retailers ： user 、 goods 、 Order …
  Educational administration system ： Student 、 achievement 、 Course …
• Extract the data item of the entity （ Data items are entity attributes ）
  goods ： commodity price , picture , describe …
  Student ： full name 、 achievement 、 Student number …
• Data items of entities designed according to the three normal forms of database design
  If the data table does not meet the three normal forms , It may be difficult to maintain , Destroying data integrity , The problem of unity
• draw E—R chart , Visually display the relationship between entities
• Database modeling ： Three line diagram for data table design 、powerdesigner,pdman
• Building database and building tables ： To write sql sentence
• Add data test database

Three paradigms

• Column cannot be subdivided
• There is no partial dependency of non key fields on key fields
  
  terms of settlement ： Divide the above table into three tables 1（ Student number 、 full name 、 Gender ）2（ Course number 、 Course name ）3（ Student number 、 Course number 、 achievement ） The third table takes student number and course number as the joint primary key
• There is no delivery dependency for non critical fields
  

solve ： Take the key field and the dependent non key field as the primary key , Check the dependencies of all non critical fields at once

draw E—R chart （ Accumulate experience in actual combat ）

Using basic graphics , Connecting lines express the relationship between entities , Properties owned, etc
Conceptual data model – Party a
Logical data model – The programmer
Physical data model – Different databases have different physical models ： You can fine tune the data model , Can directly generate database building statements with physical models –sql file , Running this file on the client can directly build the Library
Modeling tools ： You can generate database statements –sql file , It can also directly generate object-oriented code （ for example java） But in general, there is no need to , The code specifications are inconsistent

This is the end of the simple introduction to database , Thank you for watching.