Database Design Fundamentals

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Questions and Answers

What are the three main components involved in database design?

Analysis, Entity Relationship Diagram (ERD), and Relational Schema

What is the difference between a composite attribute and a multivalue attribute?

A composite attribute is a group of attributes representing a single concept, while a multivalue attribute is a single attribute that can have multiple values. (correct)

There is no difference between a composite attribute and a multivalue attribute.

A composite attribute is a single attribute that can have multiple values, while a multivalue attribute is a group of attributes representing a single concept.

A composite attribute has a dependency on other attributes, while a multivalue attribute stands alone.

Which of the following is not a type of cardinality ratio?

1:M

1:N (correct)

1:1

M:N

A weak entity is dependent on a strong entity for its existence.

True Signup and view all the answers

The process of converting an ERD into a relational schema is called ______ mapping.

Relational Schema Signup and view all the answers

What is the primary purpose of a primary key in a relational schema?

To uniquely identify each row in a table. Signup and view all the answers

What are the two main types of SQL commands used in database management?

DDL (Data Definition Language) and DML (Data Manipulation Language) Signup and view all the answers

Which of the following is not a DDL command?

update Signup and view all the answers

What is the difference between `char(n)` and `varchar(n)` data types?

<code>char(n)</code> stores fixed-length strings, reserving memory for the specified length, while <code>varchar(n)</code> stores variable-length strings, using only the actual space needed. Signup and view all the answers

Which constraint helps to enforce business rules on data within a column?

Check Signup and view all the answers

How do you add a column to an existing table using the `ALTER TABLE` command?

Use the <code>ALTER TABLE</code> command followed by <code>ADD COLUMN</code>, specifying the column name, data type, and any constraints. Signup and view all the answers

What is the purpose of the `DROP CONSTRAINT` clause in the `ALTER TABLE` command?

To remove an existing constraint from a table. Signup and view all the answers

Which DML command modifies existing data within a table?

update Signup and view all the answers

Provide the syntax for the `INSERT` command to add a new row to a table named `student`.

INSERT INTO student (column1, column2,...) VALUES (value1, value2,...); Signup and view all the answers

What does the `SELECT * FROM table_name` command do?

Retrieves all columns and rows from a table named <code>table_name</code>. Signup and view all the answers

What is the purpose of the `DISTINCT` keyword in the `SELECT` command?

To retrieve only unique values from a column. Signup and view all the answers

Which operator is used to filter data based on a specific range of values (inclusive of both endpoints)?

BETWEEN Signup and view all the answers

What is the purpose of the `ORDER BY` clause in the `SELECT` command?

To sort the retrieved data in ascending or descending order. Signup and view all the answers

What is the purpose of the `TOP` keyword in the `SELECT` command?

To retrieve a specific number of rows from a table. Signup and view all the answers

Which aggregate function calculates the average of all values in a column?

AVG Signup and view all the answers

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Study Notes

Database Design

Database design involves analysis, creating entity-relationship diagrams (ER diagrams), schema definition, and using DDL and DML.
Analysis is the first step, defining entities, attributes, and relationships.
Entities are objects, like students, instructors, courses.
Attributes are characteristics of entities, like student name, major, grade; instructor salary.
Relationships show how entities are connected, such as student-course (M:M), instructor-department (M:1), and course-section (1:M).

Attributes

Key attributes are unique identifiers (e.g., student ID, SSN).
Composite attributes are attributes with multiple parts (e.g., address includes street, city).
Multi-valued attributes have multiple values for an entity (e.g., phone numbers).
Derived attributes are calculated values based on other attributes (e.g., age from birthdate).

Relationships

Cardinality ratios describe the relationship between entities (e.g., 1:1, 1:M, M:M).
Participation constraints specify whether an entity is required in the relationship (e.g., total, partial).
Binary relationships connect two entities.
Recursive relationships occur when an entity is related back to itself (e.g., employee-supervisor).
Ternary relationships connect three entities (e.g., supplier, project, item).

Entity Types

Strong entities have their own unique identifiers.
Weak entities depend on a strong entity for their identifier (e.g., dependent, employee).

Converting ERD to Relational Schema

Entities become tables.
Attributes become columns.
Relationships become foreign keys linking tables.
A mapping algorithm converts ER models to relational tables.

SQL

SQL (Structured Query Language) is used to manipulate databases.
DDL (Data Definition Language) defines database structures (create, drop, alter).
DML (Data Manipulation Language) manipulates data (insert, update, delete, select).
Constraints are rules defining values.
Primary keys uniquely identify rows.
Foreign keys link tables using primary keys in other tables.
Constraints can include not null restrictions, uniqueness, check rules. Default values can also be defined.

Data Types

Data types define how data is stored (int, varchar, float).

DML Operations

Insert, update, and delete operations modify existing data.
Select retrieves data.

Queries and Constraints

SELECT statements retrieve data from tables.
Constraints ensure data accuracy and integrity.
Aggregate functions (count, sum, avg, min, max) calculate values across rows.
GROUP BY clause groups similar rows.

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Description

This quiz covers the essential concepts of database design, including entity-relationship diagrams, schema definition, and the use of DDL and DML. Understand the different types of attributes and relationships between entities, such as cardinality ratios and unique identifiers. Test your knowledge on the foundational principles of structuring a database effectively.

Database Design Fundamentals

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