Database Management Systems

1. Database Management Systems Entity-Relationship Model Examples

2. Notation Summary

3. name category name price makes Company Product stockprice buys employs Person name ssn address

4. Example Schema DependentOf EID Name EMPLOYEE Phone Name DEPENDENT Age Name WorksOn PROJECT Budget StartDate

5. University Example • A college contains many departments • Each department can offer any number of courses • Many instructors can work in a department • An instructor can work only in one department • For each department there is a Head • An instructor can be head of only one department • Each instructor can take any number of courses • A course can be taken by only one instructor • A student can enroll for any number of courses • Each course can have any number of students

6. Steps in ER Modeling Step 1: Identify the Entities • DEPARTMENT • STUDENT • COURSE • INSTRUCTOR

7. Steps in ER Modeling Step 2: Find the relationships • One course is enrolled by multiple students and one student enrolls for multiple courses, hence the cardinality between course and student is Many to Many. • The department offers many courses and each course belongs to only one department, hence the cardinality between department and course is One to Many. • One department has multiple instructors and one instructor belongs to one and only one department , hence the cardinality between department and instructor is one to Many. • Each department there is a “Head of department” and one instructor is “Head of department “,hence the cardinality is one to one . • One course is taught by only one instructor, but the instructor teaches many courses, hence the cardinality between course and instructor is many to one.

8. Steps in ER Modeling Step 3: Identify the key attributes • Deptname is the key attribute for the Entity “Department”, as it identifies the Department uniquely. • Course# (CourseId) is the key attribute for “Course” Entity. • Student# (Student Number) is the key attribute for “Student” Entity. • Instructor Name is the key attribute for “Instructor” Entity. Step 4: Identify other relevant attributes • For the department entity, the relevant attribute is location • For course entity, course name, duration, prerequisite • For instructor entity, room#, telephone# • For student entity, student name, date of birth

9. Steps in ER Modeling • Step 5: Draw complete E-R diagram with all attributes including Primary Key

10. E-R Diagram for a University Enterprise

11. Case Study 2 • Design a DB representing cities, counties, and states in the US: • For states, record the name, population, and state capital (a city). • For counties, record the name, the population, and the located state. • For cities, record the name, the population, the located state and the located county. • Uniqueness assumptions: • Names of states are unique. • Names of counties are unique within a state (e.g., 26 states have Washington Counties). • Cities are unique only within a state (e.g., there are 24 Springfields among the 50 states). • Some counties and cities have the same name, even within a state (e.g., Los Angeles). • All cities are located within a single county

12. Design 1: bad Co. Popu. Co. name Popu. Located cities states name Ci. Popu. Ci. name capital Problem: County Population is repeated for each city.

13. Design 2: good Co. name Co. Popu. Popu. name Located counties states Belongs-to capitals cities Ci. name Ci. Popu.

14. Case Study 3 • Design a DB consistent with the following facts. • Trains are either local trains or express trains, but never both. • A train has a unique number and an engineer. • Stations are either express stops or local stops, but never both. • A station has a unique name and an address. • All local trains stop at all stations. • Express trains stop only at express stations. • For each train and each station the train stops at, there is a time.

15. Design 1: bad number type name time addr StopsAt trains stations engineer type Problem: does not capture the constraints that express trains only stop only at express stations and local trains stop at all local stations

16. Design 2: good Lname address local stations time Lnumber engineer StopsAt2 local trains Enumber engineer express trains time StopsAt1 express stations Ename address

17. Case Study (Pine Valley Furniture Company ) • 1. The company sells a number of different furniture products. • These products are grouped into several product lines. • The identifier for a product is Product_ID, while the identifier for a product line is Product_Line_ID. • Referring to the customer invoice, we identify the following additional attributes for product: Product_Description, Product_Finish, and Unit_Price. • Another attribute fro product line is Product_Line_Name. • A product line may group any number of products, but must group at least one product. • Each product must belong to exactly one product line.

18. Case Study • 2. Customers submit orders for products The identifier fro an order is Order-ID, and another attribute is Order_Date. • A customer may submit any number of orders, but need not submit any orders. • Each order is submitted by exactly one customer. • The identifier for a customer is Customer_ID. • Other attributes include Customer_Name and Customer_Address.

19. Case Study • 3. A given customer order must request at least one product. • Any product sold by Pine Valley Furniture may not be requested on any order, or may be requested on one or more orders. • An attribute associated with each order and product is Quantity, which is the number of units requested.

20. Case Study • 4. Pine Valley Furniture has established sales territories for its customers. • Each customer does business in one or more of these sales territories. • The identifier for a sales territory is Territory_ID. • A sales territory may have any number of customers, or may not have any customers doing business.

21. Case Study • 5. Pine Valley Furniture Company has several salespersons. The identifier for a salesperson is Salesperson_ID. • Other attributes include Salesperson_Name, Salesperson_Telephone, and Salesperson_Fax. • A salesperson serves exactly one sales territory. • Each sales territory is served by one or more salespersons.

22. Case Study • 6. Each product is assembled from one or more raw materials. • The identifier for the raw material entity is Material_ID. • Other attributes include Unit_of_Measure and Unit_Price. • Each raw material may be assembled into one or more products.

23. Case Study • 7. Raw materials are supplied by vendors. • The identifier for a vendor is Vendor_ID. • Other attributes include Vendor_Name and Vendor_Address. • Each raw material can be supplied by one or more vendors. • A vendor may supply any numver of raw materials, or may not supply any raw materials to Pine Valley Furniture. • An attribute of the relationship between vendor and raw material is Unit_Price

24. Case Study • 8. Pine Valley Furniture has established a number of work centers. • The identifier for a work center is Work_Center_ID. • Another attribute is Location. Each product is produced in one or more work centers. • A work center may be used to produce any number of products, or may not be used to produce any products.

25. Case Study • 9. The company has over 100 employees. • The identifier for employee is Employee_ID. • Other attributes are Employee_Name, EmployeeAddress, and Sill. • An employee may have more than one skill. And Each skill can be mastered by many employees or none.

26. Case Study • 10: Each employee works in one or more work centers. • A work center must have at least one employee working in that center, but may have any number of employees.

27. Case Study • 11. Each employee has exactly one supervisor. • An employee who is a supervisor may supervise any number of employees, but not all employees are supervisors.

29. Design an ER schema for the following enterprise:

31. Academic Teaching Database Design an E-R schema for a database to store info about professors, courses and course sections indicating the following: • The name and employee ID number of each professor • The salary and email address(es) for each professor • How long each professor has been at the university • The course sections each professor teaches • The name, number and topic for each course offered • The section and room number for each course section • Each course section must have only one professor • Each course can have multiple sections

32. Visual View of the Database Employee ID Years Teaching Section ID Room Start Date N 1 Section Professor teaches Email N Salary First Part of Name Last 1 Number Course Topic Name

34. ER Case Study Banks Database • Each bank has a unique name. • Each branch has a number, name, address (number, street, city), and set of phones. • Customer includes their name, set of address (P.O. Box, city, zip code, country), set of phones, and social security number. • Accounts have numbers, types (e.g. saving, checking) and balance. Other branches might use the same designation for accounts. So to name an account uniquely, we need to give both the branch number to which this account belongs to and the account number. • Not all bank customers must own accounts and a customer may have at most 5 accounts in the bank. • An account must have only one customer. • A customer may have many accounts in different branches.

35. Data Modeling Case Study The following is description by a pharmacy owner: "Jack Smith catches a cold and what he suspects is a flu virus. He makes an appointment with his family doctor who confirm his diagnosis. The doctor prescribes an antibiotic and nasal decongestant tablets. Jack leaves the doctor's office and drives to his local drug store. The pharmacist packages the medication and types the labels for pill bottles. The label includes information about customer, the doctor who prescribe the drug, the drug (e.g., Penicillin), when to take it, and how often, the content of the pill (250 mg), the number of refills, expiration date, and the date of purchase." Please develop a data model for the entities and relationships within the context of pharmacy.

36. Library Case Study • When a library first receives a book from a publisher it is sent, together with the accompanying delivery note, to the library desk. Here the delivery note is checked against a file of books ordered. • If no order can be found to match the note, a letter of enquiry is sent to the publishers. If a matching order is found, a catalogue note is prepared from the details on the validated delivery note. • The catalogue note, together with the book, is sent to the registration department. The validated delivery note is sent to the accounts department where it is stored. • On receipt of an invoice from the publisher, the accounts department checks its store of delivery notes. If the corresponding delivery note is found then an instruction to pay the publishers is made, and subsequently a cheque is sent. If no corresponding delivery note is found, the invoice is stored in a pending file. 

37. A Case Study Conference centre booking system A conference centre takes bookings from clients who wish to hold courses or conferences at the centre. When clients make bookings they specify how many people are included in the booking, and of these, how many will be resident during the booking, and how many will require catered or non-catered accommodation at the centre. The centre contains a number of facilities which may be required by clients making bookings as follows: A. There are 400 bedrooms for clients who will be resident during the Course or conference. B. A maximum of 250 catered people can be handled at any one time. C. Six main lecture theatres providing seating for 200 people. D. Twenty seminar rooms each able to accommodate 25 people. E. Video conference facilities. The video conference facilities consist of four separate video conference networks. Each video conference network has a large screen based in one of the main lecture theatres, along with 3 satellite screens each of which is based in one of the seminar rooms. Draw an entity relationship diagram for the case, stating any assumptions you deem necessary.

38. Shipping company example • The London and Ireland Shipping Company PLC (LISC) was founded in 1852 and owns a fleet of cargo ships. The company had historically run passenger liners, but recent policy decisions involved the sale of all passenger-carrying vessels. The company currently has 14 vessels, including one oil tanker and one tugboat operating out of Liverpool. Most of the vessels are registered in Liberia for tax reasons. • Each ship has one or more holds divided into spaces. The holds are defined by steel bulkheads and the spaces are defined by shelf racks or other physical dividers. Sister ships, built by the same shipbuilders and to the same designs have similar names, such as Pride of Ireland, Queen of Ireland, Song of Ireland and Warrior of Ireland. Sister ships also have identical cargo storage facilities. • LISC issues contracts to agents for one or more manifests (lists of cargo items to be shipped). LISC's charges for cargo carried are based on the number of spaces the cargo requires for storage. The types of cargo typically carried by LISC include grain, coal and ores (carried only in ships equipped with bulk cargo holds). They also transport sacked grain, heavy cases, containers (which may be carried on deck), pallets and so on.

39. Shipping company example • Cargo items may take up less than one space in a hold, or one or more spaces, depending on the size of the item. A space may therefore contain several small cargo items. • The ships owned by LISC are kept as busy and as full as possible, in order to maximise the profits that each vessel makes and minimise running & operating costs. LISC's ships ply most of the seas of the world, but tend to operate mainly in the Mediterranean, the North and Mid Atlantic and the Indian Ocean. Different ships require different crew complements. • LISC intends to create a computer based information system that will be able to perform the following tasks: • • record the voyages of each ship with the start and end ports. • • record the cargo held by a ship on each voyage • • keep records of their employees and the ships they are assigned to • • producing invoices for agents and customers • • keep a record of customers' payments on invoices • • analyse the efficiency of use of cargo space and of percentage wasted cargo space for ships voyages

40. ER Case Study Television Series Database A Television network wishes to create a database to keep track of its TV series. A television series has one or more episode. Television series identified by name and season number, and includes their production company name and Num_of_Episodes ( i.e. total number of episodes in a specific season of a series ). Episode of a specific season of a series is identified by episode number and has a title and a length. No episode can exist without a corresponding television series. Also each episode has only one writer. A writer is identified by name, and also has birth date and a literary agency that represents him or her. An actor appears as a performer in a television series or a guest star on an episode. An actor is identified by name and also has a nationality and birth date. An actor plays a particular character in a television series or episode.

41. University DB Case Study • Maintain the following information about undergrad students: • Name, address, student number, date of birth, year of study, degree program (BA, BSc, BCS), concentration (Major, Honours, etc) and department of concentration. • Note: An address is composed of a street, city, province and postal code; the student number is unique for each student

42. University Case Study (cont’d) • Maintain information about departments • Name, code (CS, Phy), office phone, and faculty members • Maintain information about courses: • Course number (3753), title, description, prerequisites. • Maintain information about course sections: • Section (A, B, C), term (X1), slot #, instructor

43. University Case Study (cont’d) • Maintain information about faculty: • Name, rank, employee number, salary, office number, phone number and email address. • Note: employee number is unique • Maintain a program of study for the current year for each student: • i.e. courses that each student is enrolled in

44. Film Club Case Study: Film Club UK is a company that owns or leases a number of small cinemas in the UK. They have commissioned a database designer to design a database solution to enable them to maintain details about their cinemas and the films that they show. Note that it is possible to have two cinemas in the same location with the same name (there used to be two Odeons in Newcastle). It is also possible to have different films with the same title (for example, different versions of a Shakespeare play). Films are scheduled for one or more showings at a cinema within a ‘season’. Season details are to be notified in advance of the dates and times of showings, takings, etc. to be notified later. Any one film may have more than one season at any one cinema (for example, a cinema showing ‘The Snowman’ each Christmas). At present, all cinemas are single-screen.

45. Classroom Design Exercise Imagine we are creating a database for a dorm, which includes a cooperative kitchen. • We want to record certain information about each resident. What? • Not all residents belong to the kitchen coop. Those that do interact in various ways: • They take turns at various jobs: preparer, cleanup, buyer (for supplies). No one should have two jobs on one day. • They may or may not be vegetarian. Each meal must have at least one vegetarian entreé. • They pay fees to the coop. • For each meal, there is a menu. Each menu item requires certain ingredients, which must be on hand.

46. Airlines hold information about flights. Data is held as follows : Flight Aircraft Make Seats Airport City A-time D-time BA069 747 BA 402 LHR London - 1300 BA069 747 BA 402 ZRH Zurich 1430 1530 BA069 747 BA 402 BAH Bahrain 2300 0015 BA069 747 BA 402 SEZ Seychelles 0545 0645 BA069 747 BA 402 MRU Mauritius 0910 - SK586 DC8 DC 123 LIS Lisbon - 1500 SK586 DC8 DC 123 ZRH Zurich 1815 1855 SK586 DC8 DC 123 CPH Copenhagen 2110 2145 SK586 DC8 DC 123 ARN Stockholm 2255 - SK783 DC8 DC 123 CPH Copenhagen - 0940 SK783 DC8 DC 123 ATH Athens 1400 1500 SK783 DC8 DC 123 DAM Damascus 1700 - SK961 DC10 DC 230 CPH Copenhagen - 1810 SK961 DC10 DC 230 ATH Athens 2030 0030 SK961 DC10 DC 230 JNB Johannesburg 0935 - Example ERD from DATASTORE FLIGHTS