Modern database management solution book

22 Chapter 8 Methodology - Logical Database Design for Relational Model.... 23 Chapter 9 Methodology - Physical Database Design for Relational DBMSs .... The following tables form part o

SOLUTIONS TO REVIEW QUESTIONS

AND EXERCISES

Solutions to Review Questions and Exercises

Chapter 1 Introduction to Databases 4

Chapter 2 Database Environment 6

Chapter 3 The Relational Model 8

Chapter 4 Database Planning, Design, and Administration 12

Part Two Methodology 14 Chapter 5 Entity-Relationship Modeling 14

Chapter 6 Normalization 17

Chapter 7 Methodology - Conceptual Database Design 22

Chapter 8 Methodology - Logical Database Design for Relational Model 23

Chapter 9 Methodology - Physical Database Design for Relational DBMSs 25

Chapter 10 Conceptual Database Design Methodology - Worked Example 27

Chapter 11 Logical Database Design Methodology - Worked Example 29

Chapter 12 Physical Database Design Methodology – Worked Example 32

Part Three Database Languages 33 Chapter 13 SQL 33

Chapter 14 Advanced SQL 39

Chapter 15 QBE 46

Part Four Selected Database Issues 47 Chapter 16 Security 47

Chapter 17 Transaction Management 49

Chapter 18 Query Processing 54

Part Five Current Trends 62 Chapter 19 Distributed DBMSs - Concepts and Design 62

Chapter 20 Distributed DBMSs - Advanced Concepts 67

Chapter 21 Introduction to Object DBMSs 73

Chapter 22 Object-Oriented DBMSs 74

Chapter 23 Object-Relational DBMSs 84

Chapter 24 Web Technology and DBMSs 89Chapter 25 Data Warehousing 91Chapter 26 OLAP and Data Mining 93

Part One Background Chapter 1 Introduction to Databases

Review Questions

Some examples could be:

• A system that maintains component part details for a car manufacturer;

• An advertising company keeping details of all clients and adverts placed with them;

• A training company keeping course information and participants' details;

• An organization maintaining all sales order information

Data For end users, this constitutes all the different values connected with the various

objects/entities that are of concern to them (See also Section 1.3.3)

programs that operate on them, also called program-dataindependence (See also Sections 1.2.2 and 1.3.1)

passwords and access restrictions (See also Section 1.6)

particular constraints that are applied to the data (See also Section 1.6)

user Views can be customized, for example, field names may change, and theyalso provide a level of security preventing users from seeing certain data (Seealso Section 1.3.2)

disadvantages of this approach.

Focus was on applications for which programs would be written, and all the data required would

be stored in a file or files owned by the programs (See also Section 1.2)

Clearly, each program was responsible for only its own data, which could be repeated in otherprogram’s data files Different programs could be written in different languages, and would not beable to access another program’s files This would be true even for those programs written in thesame language, because a program needs to know the file structure before it can access it (Seealso Section 1.2.2)

approach.

Focus is now on the data first, and then the applications The structure of the data is now keptseparate from the programs that operate on the data This is held in the system catalog or datadictionary Programs can now share data, which is no longer fragmented There is also a reduction

in redundancy, and achievement of program-data independence (See also Section 1.3)

other.

See Section 1.3.3

Data Administrator See Section 1.4.1

See Section 1.6

Exercises

why? Which DBMS facilities do they find least useful and why? What do these users perceive to

be the advantages and disadvantages of the DBMS?

Select a variety of users for a particular DBMS If the users are using different DBMSs, group theanswers for the different systems, which will give an overall picture of specific systems

name, address, telephone number, preferred number of rooms and maximum rent The details should be stored in a file Enter a few records and display the details Now repeat this process but rather than writing a special program, use any DBMS that you have access to What can you conclude from these two approaches?

The program can be written in any appropriate programming language, such as Pascal,FORTRAN, C It should adhere to basic software engineering principles including being well-structured, modular, and suitably commented It is important to appreciate the process involvedeven in developing a small program such as this The DBMS facilities to structure, store, andretrieve data are used to the same effect The differences in the approaches, such as the effortinvolved, potential for extension, ability to share the data should be noted

organization? What data can you identify that needs to be represented in the database? What relationships exist between the data? What queries do you think are required?

It may be useful to review the file-based approach and the database approach here before tacklingthe first part of the exercise Careful reading and thinking about how people might use theapplications should help in carrying out the rest of the exercise

DBMS help this organization? What data can you identify that needs to be represented in the database? What relationships exist between the data?

The approach used for Exercise 1.10 should be used for this exercise also

Compare and contrast the 3 levels of this model.

See Section 2.1

An integrated collection of concepts for describing data, relationships between data andconstraints on the data in an organization (See also Section 2.3)

Object-based data models such as the entity-relationship model (see Section 2.3.1) Record-baseddata models such as the relational data model, network data model, and hierarchical data model(see Section 2.3.2)

See Section 2.3.4

Management System.

Data Storage, Retrieval and Update Authorization Services

A User-Accessible Catalog Support for Data Communication

Concurrency Control Services Services to Promote Data Independence

See also Section 2.4

Database Management System? Provide justification for your answer.

Concurrency Control Services - only single user

Authorization Services - only single user, but may be needed if different individuals are to use theDBMS at different times

Utility Services - limited in scope

Support for Data Communication - only standalone system

each facility identified in question 2.5.

Query Processor, DML Preprocessor, Data Storage, Retrieval and

Database Manager, DDL Compiler, File Manager

Services to Promote Data Independence

Utility ServicesSee also Sections 2.5 and 2.4.

approach? Compare the client-server architecture with two other architectures.

The client is a process that requires some resource, and the server provides the resource Neitherneed reside on the same machine Advantages include:

• Better performance

• Likely reduction in hardware costs

• Reduction in communication costs

• Better consistency

See also Section 2.6

See Section 2.7

Exercises

functions that we would expect to be provided by a DBMS What types of languages does each system provide? What type of architecture does each DBMS use? Check the accessibility and extensibility of the data dictionary Is it possible to export the data dictionary to another system?

To do this you will need to obtain appropriate information about each system There should bemanuals available or possibly someone in charge of each system who could supply information

that stores names and addresses in a database Modify the programs to use external, conceptual, and internal schemas What are the advantages and disadvantages of this modification?

The programs can be written in any suitable language and should be well structured andappropriately commented Two distinct files result The structures can be combined into onecontaining name, address, and tel_no, which can be the representation of both the internal andconceptual schemas The conceptual schema should be created separately with a routine to mapthe conceptual to the internal schema The two external schemas also must be created separatelywith routines to map the data between the external and the conceptual schema The two programsshould then use the appropriate external schema and routines

stores the format of the data in the database; in other words, create a data dictionary Provide an interface that makes this data dictionary accessible to external users.

Again, the program can be written in any suitable language It should then be modified to add thedata format to the original file This should not be difficult, if the original program is wellstructured The interface for other users operates on the data dictionary and is separate from theoriginal program A menu-based interface is adequate

the advantages and disadvantages of this modification?

The server should hold the data dictionary and the programs that operate on it The user interfaceshould be separate, on the client, and call the data dictionary programs

Each term defined in Section 3.2.1.

what is meant by a foreign key How do foreign keys of relations relate to candidate keys?

The primary key is the candidate key that is selected to identify tuples uniquely within a relation

A foreign key is an attribute or set of attributes within one relation that matches the candidate key

of some (possibly the same) relation

enforce these rules.

Two rules are Entity Integrity (Section 3.3.2) and Referential Integrity (Section 3.3.3)

operations in terms of the five basic operations.

Five basic operations are:

• Selection and Projection (Unary)

• Cartesian Product, Union and Set Difference (Binary)

There is also the Join, Intersection and Division operations:

• Can rewrite θ-Join in terms of the basic selection and Cartesian product operations:

when a user accesses a database through a view.

View is the dynamic result of one or more relational operations operating on the base relations toproduce another relation Base relation exists as a set of data in the database A view does notcontain any data, rather a view is defined as a query on one or more base relations and a query onthe view is translated into a query on the associated base relations

The following tables form part of a database held in a relational

DBMS:-Hotel (Hotel_No, Name, Address)

Room (Room_No, Hotel_No, Type, Price)

Booking (Hotel_No, Guest_No, Date_From, Date_To, Room_No)

Guest (Guest_No, Name, Address)

where Hotel contains hotel details and Hotel_No is the primary key

Room contains room details for each hotel and (Hotel_No, Room_No) forms the primary key Booking contains details of the bookings and the primary key comprises (Hotel_No, Guest_No,

and Date_From)

and Guest contains guest details and Guest_No is the primary key

HOTEL

σtype='S' AND price < 20(ROOM)

Πname, address(GUEST)

Πprice, type(ROOM hotel_no (σname='Grosvenor Hotel'(HOTEL)))

GUEST guest_no (σdate_from <= '01-01-99' AND date_to >= '01-01-99' (

BOOKING hotel_no (σname='Grosvenor Hotel'(HOTEL))))(substitute '01-01-99' for today’s date)

staying in the room, if the room is occupied.

(ROOM hotel_no (σname='Grosvenor Hotel'(HOTEL)) // Outer Join

Πguest.name, hotel.hotel_no, room.room_no(

(GUEST guest_no (σdate_from <= '01-01-99' AND date_to >= '01-01-99' (BOOKING hotel_no (σname='Grosvenor Hotel'(HOTEL))))(substitute '01-01-99' for today’s date)

Grosvenor Hotel.

Πguest_no, name, address(GUEST guest_no (σdate_from <= '01-01-99' AND date_to >= '01-01-99' (

BOOKING hotel_no (σname='Grosvenor Hotel'(HOTEL)))))(substitute '01-01-99' for today’s date)

details What would be the advantages of this view?

Πroom_no, hotel_no, type(ROOM hotel_no (σname='Grosvenor Hotel'(HOTEL)))Security - hides the price details from people who should not see it

Reduced complexity - a query against this view is simpler than a query against the two underlyingbase relations

Tuple Relational Calculus

(a) RANGE OF H IS HOTEL

(e) RANGE OF H IS HOTEL

RANGE OF G IS GUESTRANGE OF B IS BOOKING{G | B ((B.Date_From <= '01-01-99' AND

B.Date_To >= '01-01-99') AND(B.Guest_No = G.Guest_No) AND

∃H (B.Hotel_No = H.Hotel_No ANDH.Name = 'Grosvenor Hotel'))}

(f) Need to use Union of a relation containing all Rooms that are occupied with a relation

extended by a NULL name for all unoccupied rooms

(g) RANGE OF H IS HOTEL

RANGE OF G IS GUESTRANGE OF B IS BOOKING{G.Guest_No, G.Name, G.Address | B((B.Date_From <= '01-01-99' AND

B.Date_To >= '01-01-99') AND(B.Guest_No = G.Guest_No) AND

∃H (B.Hotel_No = H.Hotel_No ANDH.Name = 'Grosvenor Hotel'))}

Domain Relational Calculus

(a) {Hotel_No, Name, Address | ∃Hotel_No, Name, Address

(HOTEL(Hotel_No, Name, Address)}

(b) {Room_No, Hotel_No, Type, Price | ∃Room_No, Hotel_No, Type, Price

(ROOM(Room_No, Hotel_No, Type, Price) ANDType = 'S' AND Price < 20)}

(c) {Name, Address | ∃Name, Address (GUEST(Name, Address)}

(d) {Price, Type | ∃Room_No, Type, Price, Hotel_No

(ROOM(Hotel_No, Type, Price) AND

∃Name (HOTEL(Hotel_No, Name) ANDName = 'Grosvenor Hotel')}

(e) {Guest_No, Guest.Name, Guest.Address | ∃Guest_No, Name, Address,

(GUEST(Guest_No, Name, Address) AND

∃Date_From, Date_To, Hotel_No(BOOKING(Hotel_No, Guest_No, Date_From, Date_To) ANDDate_From <= '01-01-99' AND Date_To >= '01-01-99') AND

∃Name (HOTEL(Hotel_No, Name) ANDName = 'Grosvenor Hotel')))}

(f) Rest similar to above

For each relation, the primary key must not contain any nulls

Room is related to Hotel through the attribute Hotel_No Therefore, the Hotel_No in Roomshould either be null or contain the number of an existing hotel in the Hotel relation In this casestudy, it would probably be unacceptable to have a Hotel_No in Room with a null value

Booking is related to Hotel through the attribute Hotel_No Therefore, the Hotel_No in Bookingshould either be null or contain the number of an existing hotel in the Hotel relation However,because Hotel_No is also part of the primary key, a null value for this attribute would beunacceptable Similarly for Guest_No Booking is also related to Room through the attributeRoom_No

primary keys, alternate keys, foreign keys, relational integrity and views What types of relational languages does the system provide? For each of the languages provided, what are the equivalent operations for the eight relational algebra operations?

This is a small student project, the result of which is dependent on the system analyzed

See Sections 4.1 and 4.2.

See Section 4.2

See Section 4.2.3

The aims of conceptual database design are described in Section 4.3.2 and the aims of logicaldatabase design are described in Section 4.3.3

with the physical database design phase Describe the main aims of physical database design.

Physical database design is tailored to a specific DBMS, therefore it is essential the DBMS isdetermined before the physical design phase can begin The aims of physical database design aredescribed in Section 4.3.4

4.10 Assume that you are responsible for selecting a new DBMS product for a group of users in your

organization To undertake this exercise, you must first establish a set of requirements for the group and then identify a set of features that a DBMS product must provide to fulfill the requirements Describe the process of evaluating and selecting the best DBMS product.

The student should follow the approach to DBMS selection described in Section 4.6 andproduce a report that identifies a suitable DBMS product that meets the requirements of theorganization The selection should be fully justified

4.11 Assume that you are responsible for selecting a DBMS product for the Wellmeadows Hospital

case study Describe the process of evaluating and selecting the best DBMS product.

The student should follow the approach to DBMS selection described in Section 4.6 andproduce a report that identifies a suitable DBMS product that meets the requirements of the

Wellmeadows Hospital case study The selection should be fully justified and any assumptions

made about the case study should be highlighted

4.12 Investigate whether data administration and database administration exists as distinct

functional areas within your organization If identified, describe the organization, responsibilities, and tasks associated with each functional area.

The student should investigate the organization and identify whether data administration and database administration exists as distinct functional areas However, the student should be careful to note that these functions may be named differently, merged as a single function or included as part of a larger IT/IS function If identified, the student should compile a report documenting the organization, responsibilities, and tasks.

NOK

Patient

M 1

M

M M

1 1

I Requires

Has

WorksIn WorksIn

Is GoesT

Examine

Has Makes

For

AssignedTo

Receives Provides

1

Part Two Methodology Chapter 5 Entity-Relationship Modeling

Review Questions

The main purpose for developing a high-level data model is to support a user’s perception of dataand to conceal the more technical aspects associated with database design Furthermore, aconceptual data model is independent of the particular DBMS and hardware platform that is used

to implement the database

representation of these concepts.

The basic concepts of the Entity-Relationship model include entity types, relationship types, andattributes

See Section 5.1

There are two main types of restrictions on relationships called cardinality and participationconstraints

See Section 5.2

Problems may occur due to the misinterpretation of the meaning of certain relationships and theseproblems are referred to as connection traps There are two main types of connection traps calledfan traps and chasm traps

See Section 5.3

diagrammatic representation of these concepts.

The main concepts of the EER model are specialization/generalization, aggregation andcategorization However, in the accompanying textbook, we focus only on specialization/generalization and categorization, which is associated with the related concepts of entity typesdescribed as superclasses or subclasses and the process of attribute inheritance

See Section 5.4

Exercises

The University Accommodation Office Case Study

The Director of the University Accommodation Office requires you to design a database to assist with the administration of the office The requirements collection and analysis phase of the database design process based on the Director’s view has provided the following requirements specification for the Accommodation Office database.

(1) The data stored on each full-time student includes the matriculation number, name (first and last name), home address (street, city/town, postcode), date of birth, sex, category of student (for example, first year undergraduate (1UG), postgraduate (PG)), nationality, smoker (yes or no), special needs, any additional comments, current status (placed/waiting), and what course the student is studying on The student information stored relates to those currently renting a room

and those on the waiting list Students may rent a room in a university owned hall of residence or student flat When a student joins the University he or she is assigned to a member of staff who acts as his or her Advisor of Studies The Advisor of Studies is responsible for monitoring the student’s welfare and academic progress The data held on a student’s Advisor includes their full name, position, name of department, internal telephone number, and room number.

(2) Each hall of residence has a name, address, telephone number, and a hall manager who supervises the operation of the hall The halls provide only single rooms, which have a room number, place number, and monthly rent rate The place number uniquely identifies each room in all the halls controlled by the Accommodation Office and is used when renting a room to a student.

(3) The Accommodation Office also offers student flats These flats are fully furnished and provide single room accommodation for groups of 3, 4, or 5 students The information held on student flats includes a flat number, address, and the number of single bedrooms available in each flat The flat number uniquely identifies each flat Each bedroom in a flat has a monthly rent rate, a room number, and a place number The place number uniquely identifies each room available in all student flats and is used when renting a room to a student.

(4) A student may rent a room in a hall or student flat for various periods of time New lease agreements are negotiated at the start of each academic year with a minimum rental period of one semester (15 weeks) and a maximum rental period of one year, which includes Semesters 1, 2, and the Summer Semester Each individual lease agreement between a student and the Accommodation Office is uniquely identified using a lease number The data stored on each lease includes the lease number, duration of the lease (given as semesters), name, and matriculation number of the student, place number, room number, address details of the hall or student flat, the date the student wishes to enter the room, and the date the student wishes to leave the room (if known).

(5) Student flats are inspected by staff on a regular basis to ensure that the accommodation is well maintained The information recorded for each inspection is the name of the member of staff who carried out the inspection, the date of inspection, an indication of whether the property was found

to be in a satisfactory condition (yes or no), and any additional comments.

(6) Some information is also held on members of staff on the Accommodation Office and includes the staff number, name (first and last name), home address (street, city/town, postcode), date of birth, sex, position (for example, Hall Manager, Administrative Assistant, Cleaner), and location (for example, Accommodation Office or Hall).

(7) The Accommodation Office also stores a limited amount of information on the courses run by the University including the course number, course title (including year), course leader’s name, internal telephone number, and room number, and department name Each student is associated with a single course.

(8) Whenever possible, information on a student’s next-of-kin is stored which includes the name, relationship, address (street, city/town, postcode), and contact telephone number.

5.6 Create an Enhanced Entity–Relationship (EER) model to represent the data requirements of the

University Accommodation Office case study Develop the model using the following the steps:

(b) Identify relationship types and determine the cardinality and participation constraints of the relationships.

(c) Identify attributes and associate attributes with entity or relationship types.

(d) Determine candidate and primary key attributes.

(e) Specialize / generalize entity types (where appropriate).

(f) Categorize entity types (where appropriate).

(g) Draw the EER diagram.

State any assumptions you made when creating the EER model.

An example of a possible ER model for the University Accommodation Office case study is shown

below

The student should identify any ambiguities in the specification for the University AccommodationOffice and state clearly his or her assumptions For example, we may assume that we only holdinformation on a single next-of-kin per student and that some students do not provide this information

Lease

Studen

Cours Academi

Staff

NOK

Room

Accomm adatio

M1

M

1

1M

MM

11

1

∩

∩

Chapter 6 Normalization

Review Questions

When we design a database for a relational system, the main objective in developing a logical datamodel is to create an accurate representation of the data, its relationships and constraints Toachieve this objective, we must identify a suitable set of relations A technique that we can use tohelp identify such relations is called normalization Normalization is a technique for producing aset of relations with desirable properties, given the data requirements of an enterprise.Normalization supports database designers by presenting a series of tests, which can be applied toindividual relations so that a relational schema can be normalized to a specific form to prevent thepossible occurrence of update anomalies

See also Sections 6.1 and 6.4

A major aim of relational database design is to group attributes into relations so as to minimizeinformation redundancy and thereby reduce the file storage space required by the base relations.Another serious difficulty using relations that have redundant information is the problem ofupdate anomalies These can be classified as insertion, deletion, or modification anomalies.See Section 6.2

Functional dependency describes the relationship between attributes in a relation For example, if

A and B are attributes of relation R, B is functionally dependent on A (denoted A → B), if eachvalue of A in R is associated with exactly one value of B in R

Functional dependency is a property of the meaning or semantics of the attributes in a relation.The semantics indicate how the attributes relate to one another and specify the functionaldependencies between attributes When a functional dependency is present, the dependency isspecified as a constraint between the attributes

See also Section 6.3

Normalization is a formal technique for analyzing relations based on their primary key (orcandidate keys in the case of BCNF) and functional dependencies Normalization is oftenperformed as a series of tests on a relation to determine whether it satisfies or violates therequirements of a given normal form Three normal forms were initially proposed, which arecalled first (1NF), second (2NF) and third (3NF) normal form Subsequently, a stronger definition

of third normal form was introduced and is referred to as Boyce-Codd normal form (BCNF) All

of these normal forms are based on the functional dependencies among the attributes of a relation

First Normal Form (1NF) is a relation in which the intersection of each row and column containsone and only one value

Second Normal Form (2NF) is a relation that is in first normal form and every non-primary-keyattribute is fully functionally dependent on the primary key

Third Normal Form (3NF) is a relation that is in first and second normal form in which no primary-key attribute is transitively dependent on the primary key

Boyce-Codd Normal Form (BCNF) is a relation in which every determinant is a candidate key.

See also Sections 6.5 to 6.8

6.6 Describe the purpose of fourth (4NF) and fifth (5NF) normal form.

For 4NF see Section 6.11 and for 5NF see Section 6.12

Exercises

The table shown in Figure 6.25 lists dentist/patient appointment data A patient is given an appointment at

a specific time and date with a dentist located at a particular surgery On each day of patient appointments, a dentist is allocated to a specific surgery for that day.

Date Time

SurgeryNo

Figure 6.25: Lists Dentist/Patient Appointment Data.

deletion, and update anomalies.

The student should provide examples of insertion, deletion and update anomalies using the datashown in the table An example of a deletion anomaly is if we delete the details of the dentistcalled 'Helen Pearson', we also lose the appointment details of the patient called 'Ian MacKay'

normal forms State any assumptions you make about the data shown in this table.

The student should state any assumptions made about the data shown in the table For example,

we may assume that a patient is registered at only one surgery Also, a patient may have morethan one appointment on a given day

StaffNo ADate ATime StaffNo DName

PK3NF / BCNF

An agency called Instant Cover supplies part-time/temporary staff to hotels within Strathclyde Region The table shown in Figure 6.26 lists the time spent by agency staff working at various hotels The National Insurance Number (NIN) is unique for every member of staff.

Figure 6.26: Instant Cover’s Contracts.

deletion, and update anomalies.

The student should provide examples of insertion, deletion and update anomalies using the datashown in the table An example of an update anomaly is if we wish to change the name of theemployee called 'Smith J', we may only change the entry in the first row and not the last with theresult that the database becomes inconsistent

Normal Form State any assumptions you make about the data shown in this table.

The student should state any assumptions made about the data shown in the table For example,

we may assume that a hotel may be associated with one or more contracts

NIN Contract_No Hours EName H_No H_Loc

NIN Contract_No Hours

Chapter 7 Methodology - Conceptual Database Design

Review Questions

A structured approach that uses procedures, techniques, tools, and documentation aids, to supportand facilitate the process of design A design methodology consists of phases that contain steps,which guide the designer in the choice of techniques that are appropriate at each stage of theproject and also helps to plan, manage, control and evaluate database development projects.Furthermore, it is a structured approach for analyzing and modeling a set of requirements for adatabase in a standardized and organized manner

The users' involvement throughout the database design phase is critical to providing the 'correct'system In particular, the user should clarify any ambiguities in the specification that describes therequired system and also review continually the development of the database design The process

of developing the database design is repeated until the user is prepared to 'sign-off' the design asbeing a 'true' representation of the part of the enterprise that is being modeling

See Sections 7.1.3 and 7.2

7.5 Describe the main objective of conceptual database design.

See Section 7.3 Step 1

views.

User views can be identified using various methods First, by examining the data flow diagramsthat should have been produced previously to identify functional areas and possibly individualfunctions Alternatively, by interviewing users, examining procedures, reports, forms, and/orobserving the enterprise in operation

See also Section 7.3

7.7 Identify the main tasks associated with conceptual database design.

See Section 7.3

7.8 Discuss the purpose of specialization/generalization of entity types, and discuss why this is an

optional step in conceptual database design.

See Section 7.3 Step 1.6

7.9 Identify and describe the purpose of the documentation generated during conceptual database

design.

See Section 7.3 and in particular note the documentation generated at the end of each step

Chapter 8 Methodology - Logical Database Design for Relational Model

See Section 8.1 Step 2

one-to-one binary relationship types, one-to-many relationship types, multi-valued attributes, and superclass/subclass relationships.

See Section 8.1 Step 2.2

the relations derived from the model.

The logical data model can be validated using the technique of nomalization and against the transactions that the model is required to support Normalization is used to improve the model so that it satisfies various constraints that avoid unnecessary duplication of data Normalization ensures that the resultant model is a closer model of the enterprise that it serves, it is consistent, and has minimal redundancy and maximum stability.

See also Section 8.1 Step 2.3

supporting the transactions required by the user’s view.

Two possible approaches to ensure that the logical data model supports the requiredtransactions include: checking that all the information (entities, relationships and theirattributes) required by each transaction is provided by the model in documenting a description

of each transaction’s requirements, and diagrammatically representing the pathway taken byeach transaction directly on the ER diagram

See also Section 8.1 Step 2.4

8.6 Describe the purpose of integrity constraints and identify the five main types of constraints.

The main types of constraints include: There are five types of integrity constraints: required data, attribute domain constraints, entity integrity, referential integrity, and enterprise constraints.

See also Section 8.1 Step 2.6

8.7 Describe the alternative strategies that can be applied if there exists a child occurrence

referencing a parent occurrence that we wish to delete.

There are several strategies to consider when there exists a child occurrence referencing theparent occurrence that we are attempting to delete: NO ACTION, CASCADE, SET NULL,SET DEFAULT, and NO CHECK

See also Section 8.1 Step 2.6

logical model.

24See Section 8.1 Step 3 and in particular Step 3.1.

Chapter 9 Methodology - Physical Database Design for Relational DBMSs

Review Questions

carried out by different people?

Logical database design is concerned with building the data model for the organization that iscompletely independent of any DBMS Physical database design, however, is concerned withactually defining the data model using the DDL of a particular DBMS Consequently, logicaldatabase design focuses on what the data model represents, whereas physical database designfocuses on how the data model is to be implemented Different skills are required to undertakethese design phases, which are often found in different people

See Section 9.1

The inputs are the global logical data model and the data dictionary The outputs are the baserelations, integrity rules, file organization specified, secondary indexes determined, user viewsand access rules

See Section 9.3

chapter.

Step 4 Produces a relational database schema from the global logical data model This

includes integrity rules

Step 5 Determines the file organizations for the base relations This takes account of

the nature of the transactions to be carried out, which also determine wheresecondary indexes will be of use As a result of analyzing the transactions, thedesign may be altered by incorporating controlled redundancy into it

Step 6 Designs the security measures for the database implementation This includes

designing the user views and the access rules on the relations and views.Step 7 Monitors the database application systems and improves performance by

making amendments to the design as appropriate

See also Section 9.3

might we measure efficiency in this context?

This can be measured by the number of transactions that can be processed by the system in agiven time frame, or by the length of time it takes to complete one transaction, or by the amount

of disk storage taken up by the database files

See also Section 9.3 Step 5

illustrate your answer.

Generally, if overall performance needs to be improved, controlled redundancy can be introduced.See also Section 9.3 Step 5.4

Examples:

If queries on staff always required the branch address, this attribute could be posted intostaff The effect on updating would be minimal if branch data was relatively static, and itremoves a join from the query

If the number of staff for each branch was often required with branch details, a derivedattribute could be placed in branch This would remove the need to access andrepeatedly count the relevant records in staff When staff joined or left a branch, thisattribute would required updating

Chapter 10 Conceptual Database Design Methodology - Worked Example

Exercises

The Wellmeadows Hospital case study

study, described in Appendix A.

See Appendix A

10.2 List the users' requirements specification for each of these views.

The student should examine the case study in detail and identify and compile a user specificationfor the Medical Director’s and the Charge Nurse’s views As an additional task the student mayalso compile a specification for the Personnel Officer’s view

Of course to complete this exercise will require that the student makes some ascertions about theprecise requirements of each user view Any assumption should be documented along with eachview

Examples of specification for the Medical Director’s and Charge Nurse’s views are shown below

Medical Director

The Director is responsible for the overall management of the hospital and must maintain controlover the use of resources (including staff, beds, and supplies) in the provision of cost-effectivetreatment for all patients

1 The hospital is composed of many wards Each ward is managed by a Charge Nurse

The information to be held on each ward includes the ward name, number (e.g W1),phone number, location (e.g Block E), number of beds and the name of the ChargeNurse

2 Each ward is allocated staff including (e.g Charge nurse, senior and junior nurses,

doctors, consultants, auxiliaries)

3 The hospital maintains a central stock of surgical (e.g syringe, bandages) and

non-surgical (e.g plastic bags, aprons) The details of non-surgical and non-non-surgical suppliesincludes item number and name, item description, quantity in stock, re-order level, costper unit The supplies used by each ward is monitored

The hospital also maintains a stock of pharmaceutical supplies (e.g antibiotics, painkillers) The details of pharmaceutical supplies includes drug number and name,description, dosage, quantity in stock, re-order level, cost per unit The pharmaceuticalsupplies used by each ward is monitored

4 The details of the suppliers of the surgical, non-surgical and pharmaceutical items are

stored The information stored includes the supplier name and number, address, phoneand fax number

5 Patients are normally referred to the hospital for treatment by their local doctor The

details of local doctors are stored including the their name, clinic number, address andphone number

6 The details of patients referred to the hospital includes the patient number, name (first

and last name), address, phone number, date of birth, martial status, next-of-kin details(name, relationship, address and phone number)

7 When a patient is referred by their doctor to attend the hospital, the patient is given an

appointment and is examined by a consultant The details of the appointment are storedincluding the consultant’s name and number, appointment number, date, time andexamination room (e.g Room E112)

As a result of the examination, the patient is either recommended to attend the outpatientclinic or placed on a waiting list until a bed can be found in a particular ward

8 The details of outpatients are stored The information stored includes the patient details

as stated earlier (see 6) and the date and time of the appointment at the outpatient clinic

9 The details of patients currently placed in a ward and those on the waiting list for a place

on a ward are stored The information stored includes the patient details as stated earlier(see 6) and the date placed on waiting list, ward required, expected duration of stay, dateplaced in the ward and date left the ward

Charge Nurse

The Charge Nurse has overall responsibility for the management of a single ward The ChargeNurse is allocated a budget to run the ward and must ensure that all resources (staff, beds andsupplies) are used effectively in the care of patients

The Charge Nurse and other senior medical staff are responsible for the allocation of beds topatients on the waiting list

1 The information to be held on each ward includes the details of staff allocated to each

ward including the staff number, name, address, phone number, position, number ofhours worked per week and shift (e.g early, late)

2 The information stored on each patient on the waiting list includes the patient number,

name (first and last name), address, phone number, date of birth, martial status, kin details, date placed on waiting list, required ward, date placed in ward, expectedduration of stay, date left ward

next-of-3 When a patient enters the ward they are allocated a bed with a unique bed number Each

patient is prescribed medication and the details of this medication includes the patientnumber, drug number and name, units per day, start and finish date The medication(pharmaceutical supplies) given to each patient is monitored

4 Staff are allocated to work in wards, as required The Charge Nurse of each ward is

responsible for creating a staff rota which ensures that the correct complement of staffare on duty for each shift (early, late, night) Nursing staff may be specifically allocated

to patients who required specialist care

5 When required the Charge Nurse may obtain surgical, non-surgical and pharmaceutical

supplies from the central stock of supplies held by the hospital The information to bestored includes the requisition number, staff name and number, ward number, itemnumber (or drug number), quantity required, date ordered and date received

necessary to support your design.

The student should create local conceptual data models using the requirements specification forthe Medical Director and the Charge Nurse This should include an ER model representing eachuser view and the supporting documentation that describes the models Throughout the process of

design, the student should clearly state any assumptions necessary to support his or her design.

Chapter 11 Logical Database Design Methodology - Worked Example

Exercises

The Wellmeadows Hospital case study

Hospital case study identified in Exercise 10.1.

The student should refine the local conceptual models to create local logical data models based onthe Medical Director and Charge Nurse views The logical models representing each user viewshould also be validated The student should produce an ER model for each user view and thesupporting documentation that describes each model Throughout the process of design, the

student should clearly state any assumptions necessary to support his or her design.

11.2 Merge the local data models to create a global logical data model of the Wellmeadows Hospital

case study State any assumptions necessary to support your design.

Once the local data models have been validated, the student should demonstrate the viewintegration approach to create a global logical data model The student should produce an ERmodel of the global data model, representing both user views and the supporting documentationthat describes the model Throughout the process of design, the student should clearly state anyassumptions necessary to support his or her design

Wellmeadows Hospital case study.

An example of an ER model and the relational schema of the global data model of the Wellmeadows Hospital case study is shown below Note that this answer also includes the Personnel Officer’s view.

Ward (WardNo, WName, Location, TotalBeds, TelExtn, CNStaffNo)

Primary Key WardNo

Alternate Key TelExtn

Foreign Key CNStaffNo is NOT NULL references Staff(StaffNo) on delete SET DEFAULT

on update CASCADE

Staff (StaffNo, FName, LName, Address, TelNo, DOB (Date_of_Birth), Sex, (National

Insurance Number) NIN, Position, Salary, SScale, WeekHrs, ContType, TypePay)

Primary Key StaffNo

Alternate Key NIN

Qualification (QDate, QType, Institution, StaffNo)

Primary Key QType, StaffNo

Foreign Key StaffNo is NOT NULL references Staff(StaffNo) on delete CASCADE on

update CASCADE

Work_Experience (SDate, FDate, Position, OrgName, StaffNo)

Primary Key OrgName, StaffNo

Foreign Key StaffNo is NOT NULL references Staff(StaffNo) on delete CASCADE on

update CASCADE

Staff_Rota (Shift, WeekNo, StaffNo, WardNo)

Primary Key StaffNo, WeekNo

Foreign Key StaffNo is NOT NULL references Staff(StaffNo) on delete CASCADE on

update CASCADE)

Foreign Key WardNo is NOT NULL references Ward(WardNo) on delete CASCADE on

update CASCADE)

Patient (PatNo, FName, LName, Address, TelNo, DOB, Sex, MStatus, DateReg, DocName,

ClinicNo, NName, NRelationship, NAddress, NTelNo)

Primary Key PatNo

Doctor

NOK

Patient

M 1

M

M M

Form s

In Requires

WorksIn WorksIn

Is GoesTo

Examines

Has Makes

d

Foreign Key DocName, ClinicNo is NOT NULL references Doctor(DocName, ClinicNo) on delete NO ACTION on update CASCADE

Doctor (DocName, ClinicNo, Address, TelNo)

Primary Key DocName, ClinicNo

Appointment (AppNo, PatNo, ConsStaffNo, ADate, ATime, RoomNo)

Primary Key AppNo

Foreign Key PatNo is NOT NULL references Patient(PatNo) on delete NO ACTION on update CASCADE)

Foreign Key ConStaffNo is NOT NULL references Staff(StaffNo) on delete NO ACTION on update CASCADE)

OutPatient_Appointment (OutPatDate, OutPatTime, PatNo)

Primary Key OutPatDate, PatNo

Foreign Key PatNo is NOT NULL references Patient(PatNo) on delete CASCADE on update CASCADE)

InPatient_Allocation (ListDate, WardReq, Duration, PlacedDate, ExLeaveDate, ActLeaveDate,

PatNo, BedNo)

Primary Key PatNo, ListDate

Foreign Key PatNo is NOT NULL references Patient(PatNo) on delete CASCADE on update CASCADE)

Foreign Key WardReq is NOT NULL references Ward(WardNo) on delete NO ACTION on update CASCADE

Medication (PatNo, DrugNo, UnitsDay, AMethod, SDate, FDate)

Primary Key PatNo, DrugNo, SDate

Foreign Key PatNo is NOT NULL references Patient(PatNo) on delete CASCADE on update CASCADE)

Foreign Key DrugNo is NOT NULL references Pharmaceutical(DrugNo) on delete NO ACTION on update CASCADE)

Pharmaceutical (DrugNo, DName, Description, Dosage, MAdmin, QStock, RLevel, UnitCost ,

SupplierNo)

Primary Key DrugNo

Foreign Key SupplierNo is NOT NULL references Supplier(SupplierNo) on delete NO ACTION on update CASCADE

Non-Surgical/Surgical (ItemNo, IName, IDescription, QStock, RLevel, UnitCost, SupplierNo) Primary Key ItemNo

Foreign Key SupplierNo is NOT NULL references Supplier(SupplierNo) on delete NO ACTION on update CASCADE

Requisition (ReqNo, CNStaffNo, WardNo, ItemDrugNo, QuantReq, DateOrder, DateReceive) Primary Key ReqNo

Foreign Key CNStaffNo is NOT NULL references Staff(StaffNo) on delete NO ACTION on update CASCADE

Foreign Key WardNo is NOT NULL references Ward(WardNo) on delete NO ACTION on update CASCADE

Foreign Key ItemDrugNo is NOT NULL references Non-Surgical/Surgical(ItemNo) and Pharmaceutical(DrugNo) on delete NO ACTION on update CASCADE

Supplier (SupplierNo, SName, SAddress, TelNo, FaxNo)

Primary Key SupplierNo

Alternative Key TelNo

Alternative Key FaxNo

Chapter 12 Physical Database Design Methodology – Worked Example

Exercises

12.1 Create a physical database design for the logical design of the DreamHome case study

(described in Chapter 11) based on the DBMS that you have access to.

The assumption made here is that any DBMS that is being used is a relational DBMS It isimportant to know the facilities that are provided by the DBMS, and understand how to makeuse of them for physical database design Assumptions made may made, for example, on theperformance of transactions The student should produce the required documentation for thetarget DBMS

The student should implement the physical database design created in Exercise 12.1 using thetarget DBMS

DreamHome case study given in Step 7 of this chapter.

Again the student will have to investigate the functionality of the target DBMS to assesswhether the new requirements can be made If yes, the student should implement the newrequirements and also suggest further enhancements

Appendix A) based on the DBMS that you have access to.

The student should create a physical database design for the Wellmeadows Hospital case study

based on the logical design created in Exercise 11.3

The student should implement the physical database design created in Exercise 12.4 using thetarget DBMS

Part Three Database Languages

Chapter 13 SQL

Review Questions

A data definition language (DDL) for defining the database structure

A data manipulation language (DML) for retrieving and updating data

Advantages

• Satisfies ideals for database language

• (Relatively) Easy to learn

• Portability

• SQL standard exists

• Both interactive and embedded access

• Can be used by specialist and non-specialist

Disadvantages

• Impedance mismatch - mixing programming paradigms with embedded access

• Lack of orthogonality - many different ways to express some queries

• Language is becoming enormous (SQL-92 is 6 times larger than predecessor)

• Handling of nulls in aggregate functions

• Result tables are not strictly relational - can contain duplicate tuples, imposes an ordering onboth columns and rows

imposed on these clauses?

FROM Specifies the table or tables to be used

WHERE Filters the rows subject to some condition

GROUP BY Forms groups of rows with the same column value

HAVING Filters the groups subject to some condition

SELECTSpecifies which columns are to appear in the output

ORDER BY Specifies the order of the output

If the SELECT list includes an aggregate function and no GROUP BY clause is being used togroup data together, then no item in the SELECT list can include any reference to a column unlessthat column is the argument to an aggregate function

When GROUP BY is used, each item in the SELECT list must be single-valued per group.

Further, the SELECT clause may only contain:

• Column names

• Aggregate functions

• Constants

• An expression involving combinations of the above

All column names in the SELECT list must appear in the GROUP BY clause unless the name isused only in an aggregate function

do nulls affect the aggregate functions?

An aggregate function can be used only in the SELECT list and in the HAVING clause

Apart from COUNT(*), each function eliminates nulls first and operates only on the remainingnon-null values COUNT(*) counts all the rows of a table, regardless of whether nulls or duplicatevalues occur

HAVING clauses?

SQL first applies the WHERE clause Then it conceptually arranges the table based on thegrouping column(s) Next, applies the HAVING clause and finally orders the result according tothe ORDER BY clause

WHERE filters rows subject to some condition; HAVING filters groups subject to somecondition

be able to use a subquery?

With a subquery, the columns specified in the SELECT list are restricted to one table Thus,cannot use a subquery if the SELECT list contains columns from more than one table

Exercises

The following tables form part of a database held in a relational DBMS:

Hotel (Hotel_No, Name, Address)

Room (Room_No, Hotel_No, Type, Price)

Booking (Hotel_No, Guest_No, Date_From, Date_To, Room_No)

Guest (Guest_No, Name, Address)

where Hotel contains hotel details and Hotel_No is the primary key

Room contains room details for each hotel and (Hotel_No, Room_No) forms the primary key Booking contains details of the bookings and the primary key comprises (Hotel_No, Guest_No

and Date_From)

and Guest contains guest details and Guest_No is the primary key

Simple Queries

SELECT * FROM hotel;

13.8 List full details of all hotels in London.

SELECT * FROM hotel WHERE address LIKE '%London%';

Strictly speaking, this would also find rows with an address like: '10 London Avenue, New York'.13.9 List the names and addresses of all guests in London, alphabetically ordered by name.

SELECT name, address FROM guest WHERE address LIKE '%London%'

ORDER BY name;

13.10 List all double or family rooms with a price below £40.00 per night, in ascending order of price.

SELECT * FROM room WHERE price < 40 AND type IN ('D', 'F')

ORDER BY price;

(Note, ASC is the default setting)

13.11 List the bookings for which no date_to has been specified.

SELECT * FROM booking WHERE date_to IS NULL;

Aggregate Functions

13.12 How many hotels are there?

SELECT COUNT(*) FROM hotel;

13.13 What is the average price of a room?

SELECT AVG(price) FROM room;

13.14 What is the total revenue per night from all double rooms?

SELECT SUM(price) FROM room WHERE type = 'D';

13.15 How many different guests have made bookings for August?

SELECT COUNT(DISTINCT guest_no) FROM booking

WHERE (date_from <= DATE'1999-08-01' AND date_to >= DATE'1999-08-01') OR

(date_from >= DATE'1999-08-01' AND date_from <= DATE'1999-08-31');

Subqueries and Joins

13.16 List the price and type of all rooms at the Grosvenor Hotel.

SELECT price, type FROM room

WHERE hotel_no =

(SELECT hotel_no FROM hotelWHERE name = 'Grosvenor Hotel');

13.17 List all guests currently staying at the Grosvenor Hotel.

SELECT * FROM guest

13.18 List the details of all rooms at the Grosvenor Hotel, including the name of the guest staying in the

room, if the room is occupied.

SELECT r.* FROM room r LEFT JOIN

(SELECT g.name, h.hotel_no, b.room_no FROM Guest g, Booking b, Hotel hWHERE g.guest_no = b.guest_no AND b.hotel_no = h.hotel_no AND

h.name= 'Grosvenor Hotel' ANDb.date_from <= CURRENT_DATE ANDb.date_to >= CURRENT_DATE) AS XXX

ON r.hotel_no = XXX.hotel_no AND r.room_no = XXX.room_no;

13.19 What is the total income from bookings for the Grosvenor Hotel today?

SELECT SUM(price) FROM booking b, room r, hotel h

WHERE (b.date_from <= CURRENT_DATE AND

b.date_to >= CURRENT_DATE) ANDr.hotel_no = h.hotel_no and r.room_no = b.room_no;

13.20 List the rooms that are currently unoccupied at the Grosvenor Hotel.

SELECT * FROM room r

WHERE room_no NOT IN

(SELECT room_no FROM booking b, hotel hWHERE (date_from <= CURRENT_DATE AND

date_to >= CURRENT_DATE) ANDb.hotel_no = h.hotel_no AND name = 'Grosvenor Hotel');13.21 What is the lost income from unoccupied rooms at the Grosvenor Hotel?

SELECT SUM(price) FROM room r

WHERE room_no NOT IN

(SELECT room_no FROM booking b, hotel hWHERE (date_from <= CURRENT_DATE AND

date_to >= CURRENT_DATE) ANDb.hotel_no = h.hotel_no AND name = 'Grosvenor Hotel');

Grouping

13.22 List the number of rooms in each hotel.

SELECT hotel_no, COUNT(room_no) AS count FROM room

GROUP BY hotel_no;

13.23 List the number of rooms in each hotel in London.

SELECT hotel_no, COUNT(room_no) AS count FROM room r, hotel hWHERE r.hotel_no = h.hotel_no AND address LIKE '%London%'

b.date_to >= DATE'1999-08-01') OR (b.date_from >= DATE'1999-08-01' AND

b.date_from <= DATE'1999-08-31')GROUP BY hotel_no);

Yes - this is legal in SQL-92!

13.25 What is the most commonly booked room type for each hotel in London?

SELECT MAX(X)

FROM ( SELECT type, COUNT(type) AS X

FROM booking b, hotel h, room rWHERE r.room_no = b.room_no AND b.hotel_no = h.hotel_no AND

h.address LIKE '%London%'GROUP BY type);

13.26 What is the lost income from unoccupied rooms at each hotel today?

SELECT hotel_no, SUM(price) FROM room r

WHERE room_no NOT IN

(SELECT room_no FROM booking b, hotel hWHERE (date_from <= CURRENT_DATE AND

date_to >= CURRENT_DATE) ANDb.hotel_no = h.hotel_no)

GROUP BY hotel_no;

Creating and Populating Tables

13.27 Using the CREATE TABLE statement, create the Hotel, Room, Booking and Guest tables.

13.28 Insert records into each of these tables.

INSERT INTO hotel

VALUES ('H111', 'Grosvenor Hotel', 'London');

INSERT INTO room

VALUES ('1', 'H111', 'S', 72.00);

INSERT INTO guest

VALUES ('G111', 'John Smith', 'London');

INSERT INTO booking

VALUES ('H111', 'G111', DATE'1999-01-01', DATE'1999-01-02', '1');

13.29 Update the price of all rooms by 5%.

UPDATE room SET price = price*1.05;

13.30 Create a separate table with the same structure as the Booking table to hold archive records.

Using the INSERT statement, copy the records from the Booking table to the archive table relating to bookings before 1st January 1990 Delete all bookings before 1st January 1990 from the Booking table.

INSERT INTO booking1

(SELECT * FROM bookingWHERE date_to < DATE'1990-01-01');

DELETE FROM booking

WHERE date_to < DATE'1990-01-01';

General

13.31 Investigate the SQL dialect on any DBMS that you are currently using Determine the compliance

of the DBMS with the ISO standard Investigate the functionality of any extensions the DBMS supports Are there any functions not supported?

This is a small student project, the result of which is dependent on the dialect of SQL being used.13.32 Show that a query using the HAVING clause has an equivalent formulation without a HAVING

clause.

Hint: Allow the students to show that the restricted groups could have been restricted earlier with

a WHERE clause

13.33 Show that SQL is relationally complete.

Hint: Allow the students to show that each of the relational algebra operations can be expressed inSQL

ISO standard specifies the views that must be updatable in a system that conforms to the standard.Definition given in SQL-92 is that a view is updatable if and only if:

• DISTINCT is not specified; that is, duplicate rows must not be eliminated from the queryresults

• Every element in the SELECT list of the defining query is a column name (rather than aconstant, expression, or aggregate function) and no column appears more than once

• The FROM clause specifies only one table; that is, the view must have a single source tablefor which the user has the required privileges If the source table is itself a view, then thatview must satisfy these conditions This, therefore, excludes any views based on a join, union(UNION), intersection (INTERSECT), or difference (EXCEPT)

• The WHERE clause does not include any nested SELECTs that reference the table in theFROM clause

• There is no GROUP BY or HAVING clause in the defining query

In addition, every row that is added through the view must not violate the integrity constraints ofthe base table (Section 14.1.5)

Required data: NOT NULL of CREATE/ALTER TABLE

Domain constraint:CHECK clause of CREATE/ALTER TABLE andCREATE DOMAIN

Entity integrity: PRIMARY KEY (and UNIQUE) clause

of CREATE/ALTER TABLE

Referential integrity: FOREIGN KEY clause of CREATE/ALTER TABLE

Enterprise constraints: CHECK and UNIQUE clauses ofCREATE/ALTER TABLE and (CREATE) ASSERTION

Each user has an authorization identifier (allocated by DBA).

Each object has an owner Initially, only owner has access to an object but the owner can pass

privileges to carry out certain actions on to other users via the GRANT statement and take awaygiven privileges using REVOKE

SQL.

Interactive SQL: SQL statements usually input interactively from a terminal

Static and dynamic embedded SQL refers to the embedding of SQL statements in a high-levelprogramming language such as C Embedded SQL statements are changed by a preprocessorprovided with the DBMS vendor into functions calls

The basic difference between static and dynamic embedded SQL is that static SQL does not allowhost variables to be used in place of table names or column names

Exercises

Answer the following questions using the relational schema from the Exercises of Chapter 13

CREATE VIEW hotel_data(hotel_name, guest_name)

AS SELECT h.name, g.name

FROM hotel h, guest g, booking b

WHERE h.hotel_no = b.hotel_no AND g.guest_no = b.guest_no AND

b.date_from <= CURRENT_DATE ANDb.date_to >= CURRENT_DATE;

CREATE VIEW booking_out_today

AS SELECT g.guest_no, g.name, g.address, r.price*(b.date_to - b.date_from)

FROM guest g, booking b, hotel h, room rWHERE g.guest_no = b.guest_no AND r.room_no = b.room_no AND

b.hotel_no = h.hotel_no AND h.name = 'Grosvenor Hotel' ANDb.date_to = CURRENT_DATE;

access on to other users.

GRANT ALL PRIVILEGES ON hotel_data

TO manager, deputy WITH GRANT OPTION;

GRANT ALL PRIVILEGES ON booking_out_today

TO manager, deputy WITH GRANT OPTION;

14.10 Give the user Accounts SELECT access to these views Now revoke the access from this user.

GRANT SELECT ON hotel_data TO accounts;

GRANT SELECT ON booking_out_today TO accounts;

REVOKE SELECT ON hotel_data FROM accounts;

REVOKE SELECT ON booking_out_today FROM accounts;

14.11 Create the Hotel table using the Integrity Enhancement Features of SQL.

CREATE DOMAIN HOTEL_NUMBER AS CHAR(4);

CREATE TABLE hotel(

PRIMARY KEY (hotel_no));

14.12 Now create the Room, Booking, and Guest tables using the Integrity Enhancement Features of

SQL with the following constraints: