Database design

Include information management requirements （ Store and manage the required data objects in the database ） And data processing requirements ： Processing of data objects , Such as query 、 Additions and deletions 、 Statistics and analysis, etc .

Demand analysis

The output of requirement analysis is user requirement specification and data dictionary .

The most important thing in a database is a data dictionary , Contain data item , data structure , Data flow , data storage , Treatment process .

  Data flow is already the transmission path of data structure in the system . Data items or data structures form a data structure , The data items are described as follows ：

Data item	Student number
Definition	Uniquely identify each student
Alias	Student number
type	Character
length	9
Value range	0000 00 000 to 9999 99 999
Value meaning	front 4 Bits indicate the year of enrollment of the student , The first 5 The first 6 The number of your major department , The last three digits are numbered in sequence , for example 201615008
Logical relationship with other data items	The value of the student number determines the value of other data items

The data flow is described as follows ：

Data flow	Physical examination results
explain	The final report of the student's physical examination
Data stream source	physical examination （ Treatment process ）
Where does the data flow go	approval （ Treatment process ）
form	{ Student number ,{ routine blood test },{ Urine routine },{ Blood biochemistry },{ electrocardiogram },{B super },{ Other }}
Average flow	200/ God
Peak traffic	400/ God

Data storage description ：

Number	1
Data store name	Student registration form
explain	Record the basic situation of students
Input data stream	Every semester 5000
Output data stream	Every semester 5000
form	{ Student number , full name , Gender , Age ,{ Student achievement },{ Physical examination results },{ Reward and punishment records }}
Data volume	Every year, 10000 Zhang
Access method	Random access + According to the professional 、 system 、 Class printing

Process description ： yes physical design Input and Performance evaluation Principle of

Treatment process	Assign dormitories
explain	Assign student dormitories to all students
Input	Student , dormitory
Output	Dormitory arrangement
Handle	After the freshmen check in , Assign student dormitories to all freshmen
requirement	After the freshmen check in , Assign student dormitories to all freshmen , A student can only be arranged in one dormitory , The living area of each student shall not be less than 6 Square meters , Arrange the dormitory for freshmen, and the processing time shall not exceed 15 minute

  The following is EA Tool drawing data flow diagram , Search for dataflow that will do .

  notes ：EA You can treat a process as an element , Introduce to other flow charts

Conceptual structural design

ER chart 、 Extended ER chart 、UML The representation of the figure , Feeling UML The class diagram of is more appropriate and explicit .

The division principle of entities and attributes （ Classify the data received by mobile phones in the demand analysis stage 、 organization ）：

（1） The real world can be treated as an attribute , Try to treat... As an attribute

（2） As attribute , Can no longer have the properties that need to be described

（3） Attributes cannot be associated with other entities ,ER The connection shown in the figure is the connection between entities

 

  Logical structure design

take

Continuous updating