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Databases are a set of data that is which is formatted in a standard manner that is designed to be shared by

Multiple users. A database can be described by definition as “A collection of interconnected data items that may be

is processed in one of the applications software”.

A database may be described by “A collection of data that is persistent that is utilized by the program

the systems of a particular company”. A company could be one person (with an incredibly small

personal database) or a complete corporatist or similar large body (with the benefit of a massive database shared),

or any other thing in between  Denmark quality email lists.

Data

Data is the base material from which valuable information is obtained. The word “data” is plural

of Datum. Data is often utilized in singular and plural form. It’s defined as uncooked facts or

observations. It comes in a various forms, such as numbers, text, images as well as voice. Data

is a set of facts which are unorganized, but is able to be to be organized and useful.

The words Data and Information come across in everyday life and are often used interchangeably.

Examples: Weights, Prices and costs, quantity of products sold etc.

Information

The data that is processed in such a manner to enhance the understanding of the person who is using the data.

The information. Data and information are inextricably linked. Data are the raw materials that

They are then processed into final information products. The data is processed

so that it enhances the understanding of the person who is using to increase the knowledge of the person using it.

In real life, the database is today able to contain either data or other information.

Data Processing

The process of changing data into useful information is referred to as data processing.

Data processing can also be referred to by the name of information processing.

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Data that define the characteristics or properties of other types of data.

Data only becomes useful when it is used in a certain context. The main mechanism for providing

the context for data Metadata is the term used to describe data. Metadata are the data that define the characteristics, or properties of

Other data. These properties may include the definition of data or data structures, rules and data or

constraints. The Metadata provides the characteristics of data, but doesn’t include data.

It helps the database designer as well as users to know what data Exitmeans, what the data means and

What are the subtle distinctions between data items that appear to be similar. The managing of Metadata

is at a minimum as vital as understanding the data , since data with no clear significance could be

Incorrect, unclear, or confusing.

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Unit 1: Database Fundamentals

1.2 Database System Applications Notes

Databases are extensively used. Here are a few examples of database applications:

1. Banking: To provide information about customers account information, loan details, and accounts as well as banking transactions.

2. Airlines for reservations as well as schedules. Airline companies were among the first to utilize

databases distributed geographically way – terminals located around the globe

Access to through the database central system via telephone lines and other networks for data.

3. Universities: For information about students courses, registrations for classes, and grades.

4. Transactions with credit cards: for purchases made with credit cards as well as the creation of monthly

statements.

5. Telecommunication: To keep records of calls, creating monthly bills

keeping balances on prepaid call cards, and keeping records regarding the

communications networks.

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6. Financial: To keep track of information on sales, holdings and purchase of financial

instruments, such as bonds and stocks.

7. Sales for customer, product and purchase details.

8. Manufacturing: To manage the supply chain and to track the production of products in

factories, inventory of items in stores and warehouses, and requests for items.

9. Human Resources: To get details regarding salaries, employees benefits, payroll taxes and other benefits,

and also for the generation of pay checks.

1.3 Specifications of Database Approach

A common collection of data that is logically connected together with the information that is suitable to

the demands of large companies.

Program-1

data description-1

Program-2

data description-2

Program-3

data description-3

File 1

File 2.

3rd File

This section explains the fundamental difference between the conventional method for processing. It is also referred to as

processing of files, in addition to the Database method for processing data. Every operating system has

users can open, save and close files. The user can save the appropriate information within these files.

Have a look at figure 1.1 which depicts the conventional process of processing files that store the

Program and data description within an file. The information related to an application is

Files are stored in different files, such in various files such as File1, File2, etc. The files can be altered by using Program1,

Program2, etc. This was the method that was employed in the beginning.

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Database Management Systems/Managing Database

Notes This means that, without the use of a DBMS the data would be stored in several files. Any

update, the files have to be opened, and then manually search for the line , or record, then update, and finally

Save the file. This will help you understand the challenges involved in making this kind of

Information storage.

Application program 1

with Data semantics with data semantics

Manipulation

Control

……..

Application program 2

with semantics of data

Application program 3

with semantics of data

Database

Since the advent of databases The file processing method has been abandoned. Today, you

We can see in Figure 1.2 in Figure 1.2 that the data is on the disk, which controls the

DBMS. This is the way to approach Application Program-1 along with its data semantics the Application Program-1, also known as the

Program-2, along with its semantics for data and data semantics. Connect to the database that holds the actual data is stored.

And constraints can be stored in and constraints are stored through DBMS. and constraints are stored through the DBMS. DBMS is the primary control and

manipulative software modules in these applications to gain access to the data that is stored in

database.

The applications will be completely free of the program-specific code that is dependent on the system, and also get data-driven programs.

independence.

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Task: Find the different sources of databases management system.

Negatives of File Processing System

1. Catalog catalog: Catalog: DBMS the structure of the database is saved in a catalog. It also includes the

storage information with restrictions.

The DMBS software should work with any of the database software applications that are offered

The catalog contains the structure and other specifics of this application. In file processing

The definition of data forms part of an application software.

Example Record declaration in Pascal.

Structure declaration or class for structure declaration in C++.

2. Program-data independence: When processing files when changes are made to structures of

Then we could need to change the design of the program that connects to the file. If the file is in DBMS the access

Programs are written without regard to specific files. This is referred to as program-data.

independence.

The DBMS records the data in an approach that the user does not need to be aware of these particulars.

The concept is known as data abstraction. It could also be referred to as conceptual

representation.

Figure 1.2: Database Approach

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Unit 1: Database Fundamentals

3. The database could contain many users, and each user may be interested in specific Notes

View of the view of the. Views are conceptually a table. However, the table’s records do not exist.

that are stored in the database.

Take a look at the Student database, in which we have two options:

1. View: Student’ Grade in different classes. To find this information, consult the Tables Course

and Grade_Report should be created and joined as an view

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View 2. If we are looking to know about the prerequisite courses that students must learn, there are three

Tables are to be joined. These tables are nothing more than sections, student and prerequisite.

4. Processing transactions and sharing Processing and Sharing DBMS must ensure control over different users

trying to connect to the database.

Examples: Railway Reservation System with many counters.

When multiple users attempt to connect to the same app simultaneously This is what we refer to as

the situation is referred to as concurrent processing of transactions. Generally, simultaneous access is accomplished

using a basic Local Area Network (LAN). You can also purchase railway tickets on the internet

i.e. through the Internet.

1.4 Benefits of DBMS

One of the primary benefits of having a database management system is that it allows the company can

through the DBA control, centralization of control and management of the database. The administrator of the database

is the main focus of central control. Any application that requires an alteration to the organization of the structure of

Data record The DBA performs the necessary changes that do not impact other applications.

or the users of or users of.

The following are the main benefits of the use of the Database Management System (DBMS):

1. Redundancies are reduced Data Control Centralized by the DBA eliminates redundant

Duplication of data effectively reduces the total amount storage for data required. It reduces the need for storage of data.

It also removes the extra processing required to locate the needed data within the large volume of

data. Another benefit of not having duplicates is the elimination of inconsistent data

which are often found that are often found in that are often found in redundant that are often found in redundant data that are often found in redundant data.

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2. Data Independence and efficient access Application programs for databases are completely independent

of the specifics of storage and auto representation. In addition a DBMS provides efficient

storage and retrieval methods, which include support for extremely large files and index structures

Optimization of queries and.

3. Control of Data Integrity: Centralized controls will ensure that appropriate checks are carried out

within the DBMS to guarantee integrity of data. This means that the data stored in the database are secure.

It is accurate and reliable. Thus, the data values recorded for storage may not be

Verified to make sure they’re within a specific interval and conform to the proper format. Checked to ensure that they fall within the specified range and are in the correct format.

For instance, the amount for an employee’s age could be within the range between 16 and 75. For instance, the age of an employee could be between 16 and. It is also possible that it

It is important to ensure that, when there is a reference to an object, the object must be present. In the

In the case of an automated machine to teller, for instance the user isn’t allowed to transfer money

from a savings account with no existence from a savings account that is not in existence to a checking account.

4. Data Security: Data that is confidential should not be accessible to unauthorised persons. Different

Security levels could be implemented for different kinds of operations and data.

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Database Management Systems and Managing Database

Notes 5. Reducing the time to develop an application The DBMS has a number of key

Applications require certain functions that are required by applications, like functions that are required by applications, such as functions, such as crash recovery and concurrency control.

Level of query facilities level query facilities. level query facilities, etc. must be written.

6. Conflict Resolution: As the database is under supervision of the DBA the DBA should be able to resolve conflicts.

the contradicting needs of various application and user.

The DBA determines the best access method and file structure to ensure optimal performance

the critical applications that require response, while permitting applications that are less critical to continue

to access the database, although with a slower response.

7. Data Administration by providing a an unifying base for a vast amount of data, it allows for

It is used by many users. that are shared with multiple users, DBMS assists in maintenance and data administration tasks. Agood DBA is able to efficiently ensure the correctness of the database representation, the regular backups

etc.

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8. The concept of concurrent access and crash recovery A DBMS is a good fit for the concept of a transaction as well as

performs the transactions’ actions in an interleaved way to achieve high performance.

But schedules them in such so as to make sure that no conflicting operations are allowed

to operate simultaneously. Furthermore to allow for concurrent processing, the DBMS keeps a permanent record of changes made to

the database, and in the event that there’s a system malfunction it will be able to restore the database to consistency in transactions

state. In other words, the actions of incomplete transactions will be unfinished. Therefore, if each transaction is completed

A single transaction keeps the same criteria in place in the database, and then maintains the same criteria.

Following a recovery from a crash is consistent after recovery from a crash.

Task Discuss What are the benefits of using an oracle instead of access.

1.5 Negatives of DBMS

The downside that comes with this DBMS system is its overhead costs. The processing overhead that is introduced by

the DBMS to provide security and integrity as well as sharing of data can cause an impairment of the

responses and throughput times. A further cost is that of the migration process from a conventional

Separate application environments in conjunction with an integrated application.

Although centralization can reduce duplicates, the absence of duplication demands that the database is maintained.

Be adequately backup to ensure that in the event in the event of a failure, the data will be recovered in the event of failure.

Backup and recovery processes are complicated within an DBMS environment. It is an increase

in a concurrent multi-user database system. A database system requires certain amount of

monitored redundancies and duplication for easy access to the related data items.

Centralization also means that data is accessible through one source, which is the database.

This can increase the severity of security breaches, and can cause disruption of the operations of the

Organizations suffer because of downtimes and failures.

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1.6 Database Architecture

The functions of a database can be broadly classified into query processors

components and components for storage management. The query processor consists of:

1. DML Compiler transforms DML statements from an inquiry language into instructions at a low level

that the engine for query evaluation can comprehend.

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Unit 1: Database Fundamentals

2. embedded DML Pre-compiler This converts DML statements embedded in application Notes

The program must be able to make normal procedure calls within the language of host. The pre-compiler should interact

using and the DML compiler to create the correct code.

3. DDL Interpreter: It interprets DDL Stateline and stores the results in a set of tables that contain

metadata.

4. The Transaction Manager ensures the database is in a stable (correct) state.

despite any system malfunctions, and concurrent transactions are executed without

conflicting.

5. File Manager: Controls the allotment of disk storage and also the data structures that are used

to represent the information that is stored to represent information stored on disk.

6. Buffer Manager is responsible to fetch data from disk storage and transferring it to main memory, and

deciding which data to store to memory.

Additionally, certain data structures are needed in connection with the physical system’s implementation:

1. Data Files: These files contain the database itself.

2. Data Dictionary: It stores data regarding the database’s structure in the manner it is utilized

heavily.

3. Indices: It gives quick accessibility to items of data which hold certain values.

4. Statistics Data: It is statistics about the data contained in the database. It is

information that is used in the process of query processing to ch

Figure 1.3 the structure of DBMS

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Notes

Case Study Requirements Analysis

B&N’s owner B&N has considered what he would like to achieve and has provided an easy outline:

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“I would like my clients to have access to my book collection and also place an order

via using the Internet. At present, I accept orders by phone. I mostly work for corporate

Customers who contact me and provide me with my ISBN numbers for the book as well as the quantity. I will then

make a shipment of the books they’ve purchased. If I do not have enough

copies available I place an order for more copies and hold off the delivery until I receive I receive the new copies

Arrive; I’d like to send a customer’s entire order in one. My catalog contains all of the books

I also sell. Each book’s catalog will include the ISBN number the title, author, and ISBN number. purchase

cost, sales price as well as the year in which the book was released. My customers are mostly regulars,

as well as my own records that include their name, address as well as their credit card numbers. Customers who are new have

To call me first, to establish an account prior to they can access my web site. I would advise them to call me first and set up an account.

On my brand new website the customers must first identify themselves with their individual customer

identification number. After that, they will be able to browse through my catalog and place orders

online.”

The DBDudes’s experts are amazed at how fast the requirements phase went

Once they’re done, it can take several weeks of discussions (and numerous meals and lunches) to

finish the task, but then get back to their office to review the information.

1.7 Summary

The term database refers to a repository of data that can be persistent and is used by an software system that runs some

enterprise. It could be an Bank or a Hospital or an Educational Institution, a Library,

etc. The word”persistence” means that once the data in the database can be recognized by the DBMS and is subsequently able to be accessed by the DBMS, it will

Then it can be removed from the database only upon the specific request. It cannot be erased or altered because of a adverse effect, just as the program.

Language variables for language. There are many advantages to keeping the data in a the database instead of storing it in

Operating system files. A good example is the university database to illustrate this idea was used to illustrate this concept.

discussed. In the DBMS context, we talk about several individuals. For instance, the principal users are

There are DBA, Database Designers, and a variety of other users include DBA, Database Designers, and various types of. While database approaches do have some disadvantages, it is not without its limitations however, it is not the only option.

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the use of databases is vital. The most significant implications of the using databases are:

Potential for enforcing standards

Reducing the time to develop applications

Flexibility

Economically viable

Security and integrity of data

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Unit 1: Database Fundamentals

The database should not be used all the time. There are instances when you can manage your data using Notes

Access an information database.

1.8 Keywords

Data Abstraction The database management software is set of files that are interconnected and an array of data

of software that allows users to modify and access the of software that allows users to modify and access these. One of the main functions of databases is to allow users to access and modify them.

System is designed to give users an abstract understanding of data. This is known as data abstraction.

Data processing is the process of changing the facts into useful data is referred to as

Data processing. The process of processing data can also be referred to by the name of information processing.

Data The term “data” refers to the raw substance from which information is obtained.

Database: A collection of data that is logically connected together with descriptions of data

is suited to the requirements of large companies.

Metadata: Data that describes the characteristics or properties of data.

1.9 Self Assessment

Select the correct answer:

1. DBMS is the abbreviation for:

(a) Database Managerial System

(b) Database Management System

(c) Database Management Source

(d) Development Management System

2. Data processing can also be referred to as

(a) Programming data

(b) Data access

(c) Processing of information

(d) Database sourcing

3. DDL is the abbreviation for

(a) Data Development Language

(b) Document Language Document Language

(c) document definition language

(d) Data Definition Language

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Database Management System

The database.

9. In DBMS the access programs are written independent of any specific ……………………………..

10. In file processing the data definition is part of the …………………………….. program.

1.10 Review Questions

1. Define database. Define the terms used in the an environment of databases.

2. Discuss and list different Database System Applications.

3. What are the main differences between the File Processing Systems and DBMS?

4. Write about the benefits of DBMS.

5. Make short notes about the disadvantages that come with Database Management System.

6. What is Data Independence? Define the different kinds of Data Independence.

7. What are the databases languages? Define the different languages.

8. What are the duties of the role of a DBA? Give them a list and explanation.

9. What is the function of a Data user? Discuss the various kinds of users.

10. Discuss the design of DBMS.

11. Explain the various components of DBMS.

12. The history of writing for Database Systems.

Answers for Self-assessment

1. (b) 2. (c)

3. (d) 4. Indices

5. plural 6. information

7. Metadata 8. view

9. files 10. application

1.11 Additional Readings

Books C.J. Date introduction to Database Systems, Pearson Education.

Elmasri Navrate Fundamentals of Database Systems, Pearson Education.

Martin Gruber, Understanding SQL, BPB Publication, New Delhi

Peter Rob & Carlos Coronel, Database Systems Design, Implementation and

Management, 7th Edition.

Raghurama Krishnan, Johannes Gehrke, Database Management Systems, 3rd Edition,

Tata McGraw Hill.

Silberschatz, Korth, Database System Concepts, 5th Edition, McGraw Hill.

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Unit 1: Database Fundamentals

SIlberschatz-Korth-Sudarshan, Database System Concepts, 4th Edition, Tata Notes

McGraw Hill

Vai Occardi Relational Database: Theory & Practice, BPB Publication, New Delhi

Online Links www.en.wikipedia.org

www.webopedia.com

www.web-source.net

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Notes Unit 2 Notes Unit 2: Database Model of Relationships

CONTENTS

Objectives

Introduction

2.1 Relational Model

2.1.1 Relational Model Concepts

2.1.2 Solutions in the Relational Model

2.1.3 Implementation

2.1.4 Applicability to Databases

2.1.5 SQL and the Relational Model

2.1.6 Set-theoretic Formulation

2.2 Advanced Relationsal and Extensive Algebra Algebra Operations

2.2.1 Relational Algebra Expression

2.2.2 The Set Operation Relational Algebra

2.2.3 Joins

2.3 Summary

2.4 Keywords

2.5 Self-Assessment

2.6 Review Questions

2.7 Additional Readings

Objectives

After completing this unit, you’ll be able identify a relational model. the additional and extended algebraic operations

Introduction

A relational database is an array of tables that are used to store specific kinds of information. The

The invention that is a database has standardized the method the data is processed and stored.

The idea behind the relational database comes from the fundamentals of relational algebra. It is implemented as

an entire system developed by the founder of the relational database, E. F. Codd. A majority of databases are currently used

Today, we are built in the relationship system.

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2.1 Relational Model

The relational model used for managing databases is a database model that is based on a the first-order predicate

logic was first developed and first proposed in 1969 in the year 1969 by Edgar Codd.

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Unit 2 Modeling Database Model. Relational Model

Notes

The basic idea behind it is to define the database as a set of predicates that are based on an infinite set of predicate

variables, which describe restrictions on the possibilities of values and combinations. The contents

of the data at any time , is a finite representation (logic) for the data, i.e. the set of relationships,

one per predicate variable so that all predicates satisfy. Request for details to

The databases (a queries to the database) is also an example of a predicate.

2.1.1 Relational Model Concepts

The primary purpose of the model is that it provides a formal method of describing data, and

inquiries: we explicitly state what data the database holds and the details we

What you want to get it to get from it. Let the database management software manage the process of describing the data

storage structures for the data as well as retrieval processes to answer queries.

IBM adopted Codd’s ideas using the DB2 database management system. it also introduced the

SQL Data definition, query and language. Other relational management systems for databases

They are all used SQL and SQL. A table within an SQL schema for databases is akin to the concept of a

Predicate variable; the content of a table in the relation key constraints, additional constraints and

SQL queries can be compared to predicates. However, it is to be remembered it is true that SQL databases, which includes

DB2 is a deviation from the relational model in a number of specifics; Codd strongly fought against the deviations

that undermine the basic principles.

2.1.2 Alternate models for the Relational Model

Other models include the hierarchical model and the network model. Certain systems employing these models.

These architectures are still in use currently in data centers that have massive data volumes, or in areas where they are not currently used.

Systems are so complex and abstract that it would be prohibitive to switch to systems that use

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the relational model. Also to be noted are the newer object-oriented databases. However, they are not all

They are DBMS-construction kits instead of actual DBMSs. The most recent innovation is an improvement in the ObjectRelation type-Object model. This relies on the idea that any truth can be expressed using

The model is composed in which one of the binary relationships. The model is employed to model objects in Object Role Modeling

(ORM) (ORM), Notation/RDF 3 (N3) (ORM), RDF/Notation 3 in Gellish English.

Relational models were the initial model of a database. Following its definition informal models were developed.

They were developed to define the hierarchical database (the hierarchy model) as well as network databases.

(the network model (the network). Network and hierarchical databases existed prior to relational databases

Figure 2.1 2. Relational Model

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Notes were models described after the model of relational was established so as to create

A basis to compare.

2.1.3 Implementation

There have been numerous attempts to develop a complete application of the relational database

model, as first described by Codd and further explained model as originally defined by Codd and explained Date, Darwen and others however none of them have

So far, the songs have received a lot of attention. Rel is among the most recent attempts at this.

History

It was developed by E.F. (Ted) Codd as a generalized model of data. It was later reformulated by Codd as a model of

created and maintained created and maintained by Chris Date and Hugh Darwen along with others. in The Third Manifesto

(first released (first published in the year 1995) Date and Darwen show how the model of relation can be used to support

certain desirable object-oriented features.

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Codd himself, shortly after the release of his model in 1970 He proposed the concept of a three-valued logic

(True False, False, Missing or NULL) version to handle the absence of information, as well as in his

In the Relational Model for Database Management Version 2 (1990) He took it one step further by introducing an

Four-valued logic (True False but but not applicable) version. However,

These have not been implemented, probably due to their high complexity. SQL’s NULL

This was as a part of an underlying three-valued logic system however, it fell short due to

Logical errors in the standard as well as in its implementations.

The Model

The principle base assumption behind the relationshipal model is every data is represented mathematically

relations n-ary, an n-ary relationship being a subset of that of Cartesian product of two domains. In the

mathematical models, the reasoning the data is performed using two-valued predicate logic which is a reference to

there are two possible assessments for each claim one of which is either true or false (and specifically, there is there is no

Third value, such as unidentified third value, such as unknown, or not applicable both of which are connected with the

Concept of notion of NULL). Two-valued logic, as some believe, is an essential to the model of relational relationships,

Where others believe an algorithm that is based on a type of three-valued logic is still a valid option

relational.

Data is operated on using the relational calculus or algebra. These are

equivalent in terms of expressive power.

A relational database model allows developers of database to construct an logical, consistent

representation of data. Consistency is achieved through the inclusion of explicit limitations in the

Database design, often referred to as the logical schema.

The theory encapsulates a method of normalization of databases that allows for designs that have certain desirable characteristics are normalized.

The properties are available from a list of logically similar options. Access plans and

other details of operation and implementation are managed through the DBMS engine other details of operation and implementation are handled by the DBMS engine, and not

The logical model is reflected in the. This is different from the standard practices for SQL DBMSs, which the logical model is reflected in

Performance tuning usually requires modifications in the model.

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The fundamental building block of a relational system is the data type or domain which is often abbreviated to

type. Tuples are an unordered array of attributes. An attribute is a paired order of attributes.

Name and type. The value of an attribute is a valid and specific value for the kind that the attribute is. This

It could be the scalar type or a more complicated type.

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Unit 2 Modeling Database Model. Relational Model

A relation is made up of a heading and body. Headings are a collection of characteristics. A body (of notes) is a body of

relationship) is an n-tuple set. The head of the relation is the heading of every one it’s tuples.

A relation can be defined as an n-tuple set. Both in mathematics and using the database relational model

A set is an unorderly collection of items, though some DBMSs require an order on their data. A set is a collection of items that are ordered.

math, a tuple is a mathematical unit that has an order and is able to allow for duplicates. E.F. Codd originally defined

Tuples with these mathematical terms. Then the idea was considered to be one of E.F. Codd’s great insights that

using attribute names in lieu of an order is much more efficient (in the general sense) in

Computer language is built on relations. This idea is still employed in the present. However, it’s not the same,

Conceptualization has changed, but however, the name “tuple” is not. The immediate and crucial result of

This distinctive characteristic is that within the relational model, the Cartesian product is transformed into

commutative.

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A table is a commonly accepted graphic representation for a relationship and a tuple has a similar concept to the notion of row

But take note that in data-driven language SQL the columns and rows of tables are arranged.

The term “relvar” refers to a name variable that is a specific type, which is every time a particular relationship

This type of relation is assigned, even though the relation could have zero of tuples.

The principle that drives this model of relation is called the Information Principle All information is

The data is represented as values in the form of data values in. According to this Principle it is a relational database

is a collection of relvars. The results of each query is shown as an underlying relationship.

The reliability of a relational database is enforced by rules embedded into the software that

It is not used, but rather by constraint definitions, which are an element of the schema logical, and controlled by DBMS

for all kinds of applications. Constraints are generally defined using relational comparators,

of which of which one “is subsets of” that is theoretically enough. In actual use, there are a variety of helpful shorthands are available,

Are expected to be in stock and the most important ones are candidate key (really superkey)

and foreign key limitations.

Interpretation

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To fully comprehend the relationship model of data it is crucial to know the intent behind the model.

Interpretation of a relation.

A body relationship is often referred to as its extension. This is because it’s to be understood as

A representation that extends a predicate, such as the set of truthful statements that

It is possible to form a predicate by substituting each free variable of that predicate with the name (a term that denotes

something).

There is a one-to-1 connection between the parameters of the predicate as well as the attribute

names of the heading of the relation. Each tuple in the relation body gives attribute values to

Instantiate the predicate by substituting all of its variables that are free. The outcome is a predicate that

It is believed, because by the appearance of the word tuple within the relationship body to be the case. Contrariwise,

every tuple with a heading that is identical to the heading of the relation, but is not in the

Body is believed to be an illusion. This is known by the term “closed world.

For a detailed explanation of these concepts, refer to this section Set Theory Formulation.

Task Write the total amount of rules outlined to you by E.F. Codd.