Lecture 3 08/28/15. CMPSC431W: Database Management Systems. Instructor: Yu- San Lin

Transcription

1 CMPSC431W: Database Management Systems Lecture 3 08/28/15 Instructor: Yu- San Lin yusan@psu.edu Course Website: hcp:// Slides based on McGraw- Hill & Dr. Wang- Chien Lee

2 Outline Project ER model basics Ternary relauonships Key constraints 2

3 Database ApplicaUon Design Design steps: Requirement analysis Conceptual database design Logical database design Schema refinement Physical database design ApplicaUon and security design Phase 1 Phase 2 3

4 Requirement Analysis Statement of ObjecUves Brief statement made by the customer of what the objecuves of the system are Requirement Documents Expansion of State of ObjecUves Describes what the system is supposed to do, not how to do it 4

5 Conceptual Database Design ER model is used at this stage What are the enuues and relauonships? What informauon about these should we store in the database? What are the integrity constraints (or business rules) that hold? A database schema in the ER model can be represented pictorially in ER diagrams. An ER diagram can be mapped into a relauonal schema. 5

6 Project Phase 1 Due: Sep 18 th Requirement Analysis All the 11 requirements should be included and discussed Propose at least two extra funcuons Conceptual Design Complete ER diagram Report: No less than 15 pages Follow the template provided 6

7 ER Model Basic EnUty: Real- world object disunguishable from other objects. An enuty is described in DB using a set of acributes. Name SSN Lot 7

8 ER Model Basic (cont.) EnUty Set: A collecuon of similar enuues. E.g., all employees. All enuues in an enuty set have the same set of acributes. Each enuty set has a key minimal set of acributes whose value uniquely idenufy an enuty. There could be more than one ; the one designated is the (use underline to denote). Each acribute has a set of permiced values. 8

9 EnUty Sets: customer and loan customer-id customer- customer- customer- loan- amount name street city number 9

10 ER Model Basic (cont.) : associauon among two or more enuues : collecuon of similar relauonships An n- ary relauonship set R relates n enuty sets EnUty sets: RelaUonship set: Same enuty set parucipate in different relauonship sets. 10

11 ER Model Basic (cont.) A relauonship can also have descripuve acributes. Record informauon about the relauonship, rather than any parucipaung enuues. A relauonship can only be idenufied by the. 11

12 ER Model Example name dname ssn lot did budget Departments 12

13 An Instance of Works_in /1/91 1/1/91 12/9/93 1/1/97 7/31/98 5/6/99 Works- in Departments 13

14 Complex ACributes Types Composite acributes name first_name middle_name last_name How to handle these acributes? Use 14

15 Ternary RelaUonship ssn name lot since did dname budget Works_in2 Departments 15

16 Ternary RelaUonship (cont.) name ssn lot 16

17 RelaUon v.s. RelaUonship RelaUon Set of tuples; table RelaUonship Describe relauonship between enuues Both enuty sets and relauonship sets (ER model) may be represented as relauons 17

18 Key Constraints name since dname ssn lot did budget Works_in2 Departments An employee can work in many departments A department can have many employees 18

19 Key Constraints (cont.) ssn name lot since did dname budget Manages Departments Each department has at most one manager According to the key constraint on Manages 1- to- Many 19

20 Key Constraints (cont.) Mana ges Mana ges 1- to- 1 Departments Many- to- 1 Departments Mana ges Mana ges 1- to- Many Departments Many- to- Many Departments 20

21 An Instance of Manages /1/91 12/9/93 5/6/99 Manages Departments 21

22 Key constraints for Ternary RelaUonships ssn name lot since did dname budget Works_in3 Departments address LocaUons capacity 22

23 Key constraints for Ternary RelaUonships (cont.) Departments /3/93 2/2/92 3/1/92 3/1/92 Works_in Rome Delhi Paris LocaUons 23

24 QuesUon Time! Draw an ER diagram for the following applicauon: 1. Each factory has a unique id 2. More than one factory can be located in the same city 3. Each product has a unique product id 4. Each product has a color 5. A factory can produce at most one product 6. A product can be made by only one factory 7. A factory can produce a fixed quanuty of each product 24

25 QuesUon Time! Your answer: 25

26 Don t Forget Sign up the two accounts: GitHub Asana Submit your team by today 5pm Reading: Homework 1 posted on ANGEL, due Sep 11 th 26