Chapter 3

Question 1

What is the most widely used model in database management?

Answer 1

Relational model

Vendors include Microsoft, Oracle, IBM, etc.

Question 2

What are legacy systems in older database models?

Answer 2

Examples include IBM’s IMS (Information Management System) and hierarchical model

Recent competitors include object-oriented models like ObjectStore, Versant, Ontos.

Question 3

What is the object-relational model?

Answer 3

A synthesis emerging from relational and object-oriented models

Supported by Oracle, IBM DB2, MS SQL Server.

Question 4

What is a relational database?

Answer 4

A set of relations (tables)

Each relation consists of a schema and an instance.

Question 5

Define the two parts of a relation.

Answer 5

• Schema: specifies name of relation, plus name and type of each column
• Instance: a table, with rows and columns.

Question 6

What does the cardinality of a relation represent?

Answer 6

The number of rows in a relation.

Question 7

What does the degree of a relation represent?

Answer 7

The number of fields (columns) in a relation.

Question 8

True or False: All rows in a relation must be distinct.

Answer 8

True.

Question 9

What is a major strength of the relational model?

Answer 9

Supports simple, powerful querying of data.

Question 10

What is SQL?

Answer 10

A popular high-level query language used in relational databases.

Question 11

List the major revisions of SQL.

Answer 11

• SQL-86
• SQL-89 (minor revision)
• SQL-92 (major revision)
• SQL-1999 (major extensions)
• SQL-2003 (minor revision)
• SQL-2008 (minor revision)
• SQL-2011 (minor revision)
• SQL-2016 (latest release)

Question 12

What SQL command is used to create a new table?

Answer 12

CREATE TABLE

Question 13

Fill in the blank: The SQL command to insert a single tuple is _______.

Answer 13

INSERT INTO

Question 14

What SQL command is used to delete tuples from a table?

Answer 14

DELETE

Question 15

What SQL command is used to modify existing tuples?

Answer 15

UPDATE

Question 16

Write the SQL query to find all students aged 18.

Answer 16

SELECT * FROM Students S WHERE S.age=18

Question 17

What does the following SQL query compute? SELECT S.name, E.cid FROM Students S, Enrolled E WHERE S.sid=E.sid AND E.grade=’A’

Answer 17

The names of students and their course IDs for those who received an ‘A’.

Question 18

What SQL command destroys a table?

Answer 18

DROP TABLE

Question 19

What SQL command alters a table’s schema?

Answer 19

ALTER TABLE