Introduction to Databases

Question 1

What is the role of the query processor in a database system?

Answer 1

• Interprets queries
• Creates a plan to modify the database or retrieve data
• Returns query results to the application
• Performs query optimization

The query processor ensures the most efficient instructions are executed on the data.

Question 2

What does the storage manager do in a database system?

Answer 2

• Translates query processor instructions into low-level file-system commands
• Modifies or retrieves data
• Uses indexes to quickly locate data

Database sizes can range from megabytes to many terabytes.

Question 3

What is the function of the transaction manager?

Answer 3

• Ensures transactions are properly executed
• Prevents conflicts between concurrent transactions
• Restores the database to a consistent state in case of failure

The transaction manager plays a crucial role in maintaining data integrity.

Question 4

What is contained in the log of a database?

Answer 4

A complete record of all inserts, updates, and deletes processed by the database

The transaction manager writes log records before applying changes to the database.

Question 5

How does the transaction manager use log records in the event of a failure?

Answer 5

Uses log records to restore the database

This process ensures data integrity and consistency.

Question 6

What is the catalog in a database system also known as?

Answer 6

Data dictionary

It is a directory of tables, columns, indexes, and other database objects.

Question 7

What information does the catalog provide to other components?

Answer 7

Information to process and execute queries

The catalog is essential for the functioning of the database system.

Question 8

What data type is used to store integer values?

Answer 8

INT

INT is a common data type in databases for storing whole numbers.

Question 9

What data type is used to store fractional numeric values?

Answer 9

DECIMAL

DECIMAL allows for precise storage of numbers with decimal points.

Question 10

What data type is used to store textual values?

Answer 10

VARCHAR

VARCHAR is used for variable-length strings in databases.

Question 11

What data type is used to store year, month, and day?

Answer 11

DATE

DATE is specifically designed to handle date values in databases.

Question 12

The principle that physical design never affects query results is called?

Answer 12

data independence

Question 13

API

Answer 13

A library of procedures or classes that links a host programming language to a database

Question 14

A database model

Answer 14

a conceptual framework for database systems, with three parts:
1. Data structures that prescribe how data is organized.
2. Operations that manipulate data structures.
3. Rules that govern valid data.

Question 15

Data Structure Terms

Answer 15

Question 16

Mathmatical and file term for Table

Answer 16

Relation and File

Question 17

Mathmatical and file term for column

Answer 17

Attribute and Field

Question 18

Mathmatical and file term for Row

Answer 18

Tuple and Record

Question 19

Mathmatical and file term for Data Type

Answer 19

Domain and also Data Type

Question 20

What is the purpose of the Select operation in relational operations?

Answer 20

Select selects a subset of (or all) rows of a table

This operation is fundamental for retrieving specific data from a table.

Question 21

What does the Project operation do in relational operations?

Answer 21

Project selects one or more columns of a table

This operation allows for focusing on specific attributes of the data.

Question 22

What is the result of the Product operation in relational operations?

Answer 22

Product lists all combinations of rows of two tables

This operation is also known as the Cartesian product.

Question 23

How does the Join operation function in relational operations?

Answer 23

Join combines two tables by comparing related columns

This operation is essential for merging data from different tables based on a common attribute.

Question 24

What does the Union operation do in relational operations?

Answer 24

Union selects all rows of two tables

This operation combines the results of two queries, eliminating duplicates.

Question 25

What is the purpose of the **Intersect** operation in relational operations?

Answer 25

Intersect selects rows common to two tables ## Footnote This operation identifies shared data between two datasets.

Question 26

What does the **Difference** operation accomplish in relational operations?

Answer 26

Difference selects rows that appear in one table but not another ## Footnote This operation helps in identifying unique data in one dataset.

Question 27

What is the function of the **Rename** operation in relational operations?

Answer 27

Rename changes a table name ## Footnote This operation is useful for improving clarity or avoiding naming conflicts.

Question 28

What does the **Aggregate** operation compute in relational operations?

Answer 28

Aggregate computes functions over multiple table rows, such as sum and count ## Footnote This operation is essential for summarizing data.

Question 29

What are **relational rules** in the context of the relational model?

Answer 29

* Unique primary key * Unique column names * No duplicate rows ## Footnote Relational rules govern data in every relational database.

Question 30

What does a **unique primary key** ensure in a relational database?

Answer 30

Values may not repeat ## Footnote All tables must have a primary key column or group of columns.

Question 31

True or false: Different columns of the same table can have the **same name**.

Answer 31

FALSE ## Footnote Each column in a table must have a unique name.

Question 32

What does the rule of **no duplicate rows** state in a relational database?

Answer 32

No two rows of the same table have identical values in all columns ## Footnote This ensures data integrity within the table.