Chapter 2

Question 1

A database model is a conceptual framework for database systems, with three parts:

Answer 1

Data structures that prescribe how data is organized.
Operations that manipulate data structures.
Rules that govern valid data.

Question 2

A table has

Answer 2

name, a fixed tuple of columns, and a varying set of rows

Question 3

A column has

Answer 3

name and a data type.

Question 4

A row is

Answer 4

unnamed tuple of values. Each value corresponds to a column and belongs to the column’s data type

Question 5

A data type is a

Answer 5

named set of values, from which column values are drawn.

Question 6

Database/Mathematics/File System
Table/Relation/File

Answer 6

A container for storing related data.

Question 7

Database/Mathematics/File System
Row/Tuple/Record

Answer 7

A single entry or instance in the container.

Question 8

Database/Mathematics/File System
Column/Attribute/Field

Answer 8

A property or characteristic of the entity.

Question 9

Database/Mathematics/File System
Data Type/Domain/Data Type

Answer 9

Specifies valid values for data.

Question 10

Relational operations - Select

Answer 10

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

Question 11

Relational operations - Project

Answer 11

selects one or more columns of a table

Question 12

Relational operations - Product

Answer 12

lists all combinations of rows of two tables

Question 13

Relational operations - Join

Answer 13

combines two tables by comparing related columns

Question 14

Relational operations - Union

Answer 14

selects all rows of two tables

Question 15

Relational operations - Intersect

Answer 15

selects rows common to two tables.

Question 16

Relational operations - Difference

Answer 16

selects rows that appear in one table but not another

Question 17

Relational operations - Rename

Answer 17

changes a table name

Question 18

Relational operations - Aggregate

Answer 18

computes functions over multiple table rows, such as sum and count

Question 19

Relational rules -Unique primary key

Answer 19

All tables have a primary key column, or group of columns, in which values may not repeat

Question 20

Relational rules - Unique column names

Answer 20

Different columns of the same table have different names.

Question 21

Relational rules -No duplicate rows

Answer 21

No two rows of the same table have identical values in all columns

Question 22

sublanguages-Data Definition Language

Answer 22

defines database structure

Question 23

sublanguages-Data Query Language

Answer 23

retrieves data

Question 24

sublanguages-Data Manipulation
Language

Answer 24

inserts, updates, and deletes
data.

Question 25

sublanguages-Data Transaction Language

Answer 25

manages transactions

Question 26

sublanguages-Data Control Language

Answer 26

Data Control Language

Question 27

Language elements -Literal

Answer 27

Explicit value such as a character string or number. String literals are enclosed in either single or double quotes

Question 28

Language elements -Keyword

Answer 28

Word with a special meaning for the language processor. Keywords are defined by the database system

Question 29

Language elements -Identifier

Answer 29

Name of a database object, such as a column, table, or database. Identifiers are specified by the programmer

Question 30

Language elements -Expression

Answer 30

Sequence of literals, identifiers, and operations that evaluate to a single value

Question 31

Language elements -Comment

Answer 31

Text that is ignored by the language processor. Single-line comments begin with-- followed by a space. Multi-line comments are enclosed in/ * and */.

Question 32

Syntax definitions -UPPERCASE

Answer 32

text indicates SQL keywords.

Question 33

Syntax definitions -lower case

Answer 33

text indicates an identifier or expression provided by the user. In some cases, lower case text is a placeholder for a complex construction, defined elsewhere.

Question 34

Syntax definitions -Square brackets []

Answer 34

enclose an optional language element

Question 35

Syntax definitions - Curly braces {}

Answer 35

enclose a series of alternative language elements, separated by vertical bars. One, and only one, of the alternatives must be included in the statement.

Question 36

Syntax definitions - Ellipsis ...

Answer 36

indicates that the preceding language element may be repeated

Question 37

Syntax definitions - Parentheses ()

Answer 37

and commas are literal symbols. Unlike brackets and braces, parentheses and commas appear in SQL statements exactly as written in the syntax definition.