DCIT 55 - Relational Database Concepts Review

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Questions and Answers

What is a common misconception about strong relationships in the context of databases?

It is primarily based on the quantity of data stored (correct)

It always involves a one-to-one relationship

It doesn't help in establishing connections between tables

It is unrelated to primary keys

In the ER Model, what does cardinality express?

The maximum number of entities associated with one occurrence of the related entity (correct)

The type of data stored in the database

The size of the database

The number of data attributes in the database

Which component is NOT considered one of the three basic notions of the ER Model?

Entities

Attributes

Relationships

Cardinality (correct)

What is a common misconception about the main parts of a database system?

Hardware is the most crucial part Signup and view all the answers

Which of the following is NOT one of the nine functions of a Database Management System (DBMS)?

Query performance optimization Signup and view all the answers

What type of attributes can have only a single value?

Single-Valued Attributes Signup and view all the answers

What is the purpose of a Project operation in a database?

Yields a vertical subset of a table Signup and view all the answers

What is the main function of an ER diagram in a database system?

It represents a conceptual database viewed by an end-user Signup and view all the answers

What characterizes a single-user database?

Supports only one user at a time Signup and view all the answers

What is a Transaction in the context of a database?

A set of operations that performs a particular task Signup and view all the answers

What is the significance of a Centralized database?

Supports data located at a single site Signup and view all the answers

What is a Primary Key?

An attribute that uniquely identifies any given entity Signup and view all the answers

What is the purpose of a SAVEPOINT in database transactions?

To mark and save the current point in the processing of a transaction Signup and view all the answers

In database terminology, what does the term 'Domain' refer to?

An attribute's set of possible values Signup and view all the answers

What does the Implicit Commit Command do in the context of databases?

Forces a COMMIT to occur automatically without user intervention Signup and view all the answers

What is Connectivity in databases?

A command used to describe the relationship classification Signup and view all the answers

What is the purpose of the Relational Model in database management?

To enable programmers to view data logically rather than physically Signup and view all the answers

What type of anomaly occurs when entering new records?

Insertion anomalies Signup and view all the answers

What is the purpose of the ROLLBACK command in a database system?

Terminate the current transaction and undo changes Signup and view all the answers

What does the Natural join do when linking tables?

Selects rows with common values in common attribute(s) Signup and view all the answers

What is the definition of a Super key in a database context?

Any attribute that identifies rows uniquely Signup and view all the answers

In a multiple-user database system, what does the abbreviation TCL stand for?

Transaction Control Language Signup and view all the answers

How does the Equijoin link tables together?

By comparing specified columns with an equality condition Signup and view all the answers

Study Notes

ER Model and Relationships

Strong relationships exist when the PK of the related entity contains the PK component of the parent entity.
Weak relationships exist if the PK of the related entity does not contain the PK component of the parent entity.
Existence dependence exists in the database only when it is associated with another related entity occurrence.
Existence independence is an entity that can exist apart from one or more related entities.

Database System Components

Five main parts of a database system:
- Data
- People
- Hardware
- Software
- Process

Relational Algebra Operators

Eight relational algebra operators:
- Union
- Intersect
- Difference
- Divide
- Product
- Select
- Join
- Project

Database Management System (DBMS)

Nine functions of DBMS:
- Data dictionary management
- Data storage management
- Data transformation and presentation
- Security management
- Multiuser access control
- Backup and recovery management
- Data integrity management
- Database access languages and application programming interfaces
- Database communication interfaces

Database Concepts

Primary key: an attribute that uniquely identifies any given entity.
Composite key: composed of more than one attribute.
Foreign key: an attribute whose values match primary key values in the related table.
Secondary key: key used strictly for data retrieval purposes.
Candidate key: a superkey without redundancies.
Super key: any key that uniquely identifies each row.

Data and Information

Data: raw material used to derive information.
Information: a product derived from data.

Database Operations

Transaction: a set of database operations that performs a particular task.
COMMIT: used to permanently save any transaction into the database.
SAVEPOINT: marks and saves the current point in the processing of a transaction.
ROLLBACK: terminates the current transaction and undoes any changes made during the transaction.

Join Operations

Natural join: links tables by selecting only rows with common values in their common attribute(s).
Theta join: applicable if any other comparison operator is used.
Equijoin: links tables on the basis of an equality condition that compares specified columns of each table.
Outer join: the matched pairs are retained, and any unmatched values in the other table are left null.

Data Warehouse and Database

Database: a collection of interrelated data.
Data warehouse: stores data used to generate information required to make tactical or strategic decisions.

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Description

Test your knowledge of Relational Database Concepts including ER model, attributes, anomalies, and database types with this quiz. Topics include ER diagrams, derived/computed attributes, single-valued attributes, multivalued attributes, deletion anomalies, single-user databases, and transactions.