Data Modeling, Queries

Question 1

What is data modeling?

Answer 1

A technique to document a database management system using diagrams and symbols.

Question 2

What does ERD stand for?

Answer 2

Entity Relationship Diagram.

Question 3

What is the primary purpose of an ERD?

Answer 3

To provide a graphical representation of data requirements for a database.

Question 4

What are the three components of an ERD?

Answer 4

• Entities
• Attributes
• Relationships

Question 5

Define ‘Entities’ in the context of ERDs.

Answer 5

The basic objects of ERDs, usually represented as tables.

Question 6

List the five classes of entities.

Answer 6

• Concepts
• Location
• Roles
• Events
• Things

Question 7

What is an instance of an entity?

Answer 7

A specific example of an entity that becomes a record or row in a table.

Question 8

What are ‘Attributes’ in an ERD?

Answer 8

Facts or descriptions of entities that become the columns of the table.

Question 9

What is a primary key?

Answer 9

An attribute or set of attributes that uniquely identifies an instance of an entity.

Question 10

Can a table have more than one primary key?

Answer 10

No, a table can have only one primary key.

Question 11

Define ‘Foreign Key’.

Answer 11

A key used to link two tables together, typically the primary key from one table inserted into another.

Question 12

What are Relationships in an ERD?

Answer 12

Associations between the entities, often described with verbs.

Question 13

What notation is used to represent relationships in ERDs?

Answer 13

Crow’s Foot notation.

Question 14

Describe a One to One Relationship (1:1).

Answer 14

A single entity instance in one entity class is related to a single entity instance in another entity class.

Question 15

Describe a One to Many Relationship (1:M).

Answer 15

A single entity instance in one entity class is related to multiple entity instances in another entity class.

Question 16

Describe a Many to Many Relationship (M:M).

Answer 16

Each entity instance in one entity class is related to multiple entity instances in another entity class and vice versa.

Question 17

What is the purpose of queries in health data?

Answer 17

• Efficient data retrieval
• Improved decision making

Question 18

List types of queries in MS Access.

Answer 18

• Select Query
• Action Query
• Parameter Query
• Crosstab Query
• SQL Query

Question 19

What is a Select Query?

Answer 19

Retrieves data based on specific conditions.

Question 20

What is an Action Query?

Answer 20

Updates, deletes, or adds data.

Question 21

What does SQL stand for?

Answer 21

Structured Query Language.

Question 22

What is the primary use of SQL?

Answer 22

To communicate with databases.

Question 23

What is the difference between SQL and MS Access?

Answer 23

• MS Access: User-friendly interface for database management
• SQL: Text-based commands for advanced data retrieval

Question 24

What is the basic structure of a SELECT statement?

Answer 24

• SELECT [columns]
• FROM [table]

Question 25

What clause is used to filter results in SQL?

Answer 25

WHERE clause.

Question 26

How do you sort query results in SQL?

Answer 26

Use the ORDER BY clause.

Question 27

What is the purpose of the GROUP BY clause?

Answer 27

To group rows that have the same values in specified columns.

Question 28

Fill in the blank: A _______ is used to create a new table from query results.

Answer 28

Make-Table Query

Question 29

Fill in the blank: A _______ Query combines results from multiple Select Queries.

Answer 29

Union

Question 30

True or False: A foreign key can be null.

Answer 30

True