Database Application

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Exercise 3.18: Show an alternative design for the attribute described below, that uses only entity types (including weak entity types, if needed) and relationship types.

 

{ PreviousEducation ( CollegeName, StartDate, EndDate,

{ Degree (DegreeName, Month, Year) },

{ Transcript (CourseName, Semester, Year, Grade) } ) }

 

Exercise 3.19: Consider the ER diagram in Figure 3.21, which shows a simplified schema for an airline reservations system. Extract from the ER diagram the requirements and constraints that produced this schema. Try to be as precise as possible in your requirements and constraints specification.

 

MODULE 5

Exercise 5.11: Suppose that each of the following Update operations is applied directly to the database state shown in Figure 5.6. Discuss all integrity constraints violated by each operation, if any, and the different ways of enforcing these constraints.

 

Insert <‘Robert’, ‘F’, ‘Scott’, ‘943775543’, ‘1972-06-21’, ‘2365 Newcastle Rd, Bellaire, TX’, M, 58000, ‘888665555’, 1> into EMPLOYEE.

 

Insert <‘ProductA’, 4, ‘Bellaire’, 2> into PROJECT.

 

Insert <‘Production’, 4, ‘943775543’, ‘2007-10-01’> into DEPARTMENT.

 

Insert <‘677678989’, NULL, ‘40.0’> into WORKS_ON.

 

Insert <‘453453453’, ‘John’, ‘M’, ‘1990-12-12’, ‘spouse’> into DEPENDENT.

 

Delete the WORKS_ON tuples with Essn = ‘333445555’.

 

Delete the EMPLOYEE tuple with Ssn = ‘987654321’.

 

Delete the PROJECT tuple with Pname = ‘ProductX’.

 

Modify the Mgr_ssn and Mgr_start_date of the DEPARTMENT tuple with Dnumber = 5 to ‘123456789’ and ‘2007-10-01’, respectively.

 

Modify the Super_ssn attribute of the EMPLOYEE tuple with Ssn = ‘999887777’ to ‘943775543’.

 

Modify the Hours attribute of the WORKS_ON tuple with Essn = ‘999887777’ and Pno = 10 to ‘5.0’.

 

 

Exercise 5.13: Consider the relation CLASS(Course#, Univ_Section#, Instructor_name, Semester, Building_code, Room#, Time_period, Weekdays, Credit_hours). This represents classes taught in a university, with unique Univ_section#s. Identify what you think should be various candidate keys, and write in your own words the conditions or assumptions under which each candidate key would be valid.

 

Exercise 5.14: Consider the following six relations for an order-processing database application in a company:

 

CUSTOMER(Cust#, Cname, City)

ORDER(Order#, Odate, Cust#, Ord_amt)

ORDER_ITEM(Order#, Item#, Qty)

ITEM(Item#, Unit_price)

SHIPMENT(Order#, Warehouse#, Ship_date)

WAREHOUSE(Warehouse#, City)

 

Here, Ord_amt refers to total dollar amount of an order; Odate is the date the order was placed; and Ship_date is the date an order (or part of an order) is shipped from the warehouse. Assume that an order can be shipped from several warehouses. Specify the foreign keys for this schema, stating any assumptions you make. What other constraints can you think of for this database?

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