Phases of Database Design

Transcription

1 Database Design

2 Phases of Database Design Data Requirements Specification of requirements and results Conceptual Design Conceptual Schema Logical Design Logical Schema Physical Design Conceptual design begins with the collection of requirements and results needed from the database (ER Diag.) Logical schema is a description of the structure of the database (Relational, etwork, etc.) Physical schema is a description of the implementation (programs, tables, dictionaries, catalogs Physical Schema 2

3 Models A data model is a collection of objects that can be used to represent data and its structure, information, operations to manipulate the data Conceptual models are tools for representing reality at a very high-level of abstraction Logical models are data descriptions that can be processed by computers 3

4 Conceptual model: Entity-Relationship Diagrams Entities represent classes of real-world objects. Person, Students, Projects, Courses are entities of a University database Relationships represent interactions between two or more entities Lives_In Person City Is_Born_In 4

5 Example: Every employee works in at least one project Every project has employees working on it. EMPLOYEE SS ame Salary WORKS_O PROJECT ame Code 5

6 Higher-Order Relationships A relationship may involve more than two entities Course Meets Classroom Day 6

7 Recursive relationships Relationships could be mapped from one entity to itself Manager_Of Employee Manages Subordinate_To 7

8 Attributes Attributes represent elementary properties of the entities or relationships. The stored data will be kept as values of the attributes Lives_In PERSO Ssn ame Profession Moving_Date Birth_Date CITY ame Country Elevation Population Is_Born_In 8

9 Generalizations An entity could be seen from many different viewpoints Each viewpoint defines a set of roles in a generalization Example below uses SEX to classify the object Person PERSO Ssn ame Address MA Draft_Status FEMALE Maiden_ame 9

10 Generalizations A classification could be disjoint or overlapping An entity could have more than one classification PERSO Ssn ame Address SEX JOB MA Draft_Status FEMALE Maiden_ame Full_Time Annual_Salary Department Part_Time Hour_Rate Weekly_Hours 0

11 Example: Department Store /2 A department store operates in several cities In a city there is one headquarter coordinating the local operations A city may have several stores Stores hold any amount of items Customers place their orders for any number of items to a given store GOAL: Optimize shopping in each city

12 Example: Department Store 2/2 STORES Store ID Address Manager ID LOCATED I CITIES City ame State HeadQtr Address HOLD Qty Held I-CITIES Qty_in_cities CUSTOMER Customer ame Address Phone umber ITEMS Item ID Description Size Color ORDERS ITEMS ORDERED Order umber Qty Ordered Order Date PLACE 2

13 Example: University Database Professors work for only one department Departments have many professors Each course is taught by only one professor Students make a plan or program of study A course could meet in several rooms/times Graduate students must have an advisor Cities are categorized as resident/birthplace Visiting prof. need an End/Start date 3

14 4 University Database University database BIRTH_PLACE CITY ame State PERSO Lastame Age PROFESSOR TenureStatus Title STUDET DEPARTMET ame Phone Belongs_To EROLLED Semester Grade PLAED Semester GRADUATE_STUDET ADVISED_BY VISITIG_ PROFESSOR Start_Appointment End_Appointment COURSE Title Description Credits TAUGHT_BY Semester MEETS ROOM Roomumber Building TIME Day Hour RESIDET

15 Soccer Database A team has players, one coach, fans Teams play according to a schedule Teams need to practice in a Stadium Attendance and scores must be recorded 5

16 Soccer Database PERSO Ssn ame Address FA ame Address Favorite Bar PLAYER Uniform_Size Shoe_Size COACH Personal Record Years Experience SUPPORTS PLAYS _FOR MAAGES TEAM ame Location Phone PLAY_ AGAIST PRACTICES ATTEDS GAME umber Attendance Final Score Date TAKES PLACE AT STADIUM ame Address Capacity 6

17 Research Project Database Some employees are researchers Every project has a leader investigator Every project must be funded by an agency A project may include several topics A topic could appear in several projects Researchers must produce report(s) Each employee must have a supervisor 7

18 Research Projects Database RESEARCH REPORT umber Title SUPERVISE S ADDRESSES PRODUCES RESEARCH TOPIC Code ame O RESEARCH PROJECT ame Code PRICIPAL IVESTIGATOR EMPLOYEE SS ame Title WORKS _O FUDED_BY Amount Date Grant# AGECY ame Address Contact Person 8

19 Contract-Supplies System /3 A company negotiates contracts with suppliers to provide certain amount of items at a fixed price Orders are placed against any of the already negotiated contracts A contract could provide items to any number of orders 9

20 Contract-Supplies System 2/3 An order may include any number of items negotiated in the contract Orders should not exceed the maximum amount of items quoted in the contract All items in an order must be provided as part of a single contract and a single project 20

21 Contract-Supplies System 3/3 SUPPLIERS Supplier umber ame Address EGOTIATE Date of Contract PROJECTS Project umber Project Data COTRACTS Contract umber Text SUPPLIED AS EEDED BY TO SUPPLY Contract Price Contract Amount ITEMS Item umber Description MADE OF Order QTY ORDERS Order umber Date Required Date Completed 2

22 Manufacturing: Requisitions /3 Projects are broken into tasks Tasks are assigned to departments A task is created for one project and assigned to one department Requisitions are made for projects Each requisition could ask for any number of items 22

23 Manufacturing: Requisitions 2/3 Each requisition is for one project and is made to one supplier Items could be: equipment or materials and are coded in a similar way Suppliers send periodic price notices to advise the company of any changes in their prices 23

24 Manufacturing: Requisitions 3/3 PROJECTS Project umber Project Data MADE OF TASKS Task umber Task Data REQUESTS FOR REQUISITIO Item umber Qty Requested FROM SUPPLIERS Supplier umber Supplier Data COTAIS SEDS ITEMS Item umber Item Data CHAGES PRICE ADVICE Price Effective Date EQUIPMET ITEM Code Description MATERIAL ITEM Code Description Weight Container 24

25 Job-Shop Accounting System /4 The system is used by a company that manufactures special-purpose assemblies for customers To manufacture assemblies the company creates a sequence of processes (steps) Each process is supervised by a department Assume there are three type of processes: PAIT, FIT, CUT 25

26 Job-Shop Accounting System 2/4 During manufacturing an assembly could pass through any sequence of processes, in any order; it may pass through the same process more than once A unique Job# is given to any new assembly. Costs and started-terminated dates must be recorded 26

27 Job-Shop Accounting System 3/4 An accounting system is used to keep track expenditure for each: DEPT, PROCESS, ASSEMBLY As a job proceeds, cost transactions can be recorded against it. 27

28 Job-Shop Accounting System 4/4 CUSTOMER S Customer ID Address ACCOUTS Account ID Date Established A ORDERS ASSEMBLIE S Assembly ID Date Ordered Details MADE AS TRASACTIOS ACTIVITY T T2 T3 ASSEMBLY ACCOUTS Account Details DEPT ACCOUTS Account 2 Details A2 DEPARTMET S Dept umber Dept Data PROCESS ACCOUTS Account 3 Details CUT JOBS Cut Job ID Machine type used Material used Laor time JOBS Job umber Starting Date Ending Date Total Cost FIT JOBS Fit Job ID Labor time PAIT JOBS Paint Job ID Color Volume Labor time USES PAIT PROC Paint Proc ID Paint Method USED I PROCESSES Process ID Process Data FIT PROC Fit Proc ID Fit Type A3 CUT PROC Cut Proc ID Cuttong Type Machine Type 28