Ch3

Question 1

Entity

Answer 1

A person, place, event, or thing for which we intend to collect data

Question 2

Attribute

Answer 2

Describes a characteristics of an entity

Question 3

Entity Set

Answer 3

A group of entities of the same type

Question 4

Table/Relation

Answer 4

Contains a group of related entities

Question 5

Rows and Columns

Answer 5

A table is composed of this

Question 6

Row

Answer 6

Tuple

Question 7

Each __ represents a single __ within the entity set

Answer 7

Row, entity

Question 8

Each ___ represents an ___ and is identified by a district name

Answer 8

Column, Attribute

Question 9

Each row/column intersection represents a single data value

Answer 9

Atomic

Question 10

Cardinality

Answer 10

The number of tuples in a table

Question 11

Degree

Answer 11

The number of column is known as

Question 12

Attribute Domain

Answer 12

All values in a column must conform to the same data format (type) and must be within a specified range

Question 13

Changing the order of the rows and/or column___

Answer 13

Does not change the table

Question 14

Key

Answer 14

Consists of one or more attributes that determines other attributes within an entity

Question 15

Composite key

Answer 15

A key that composed of more than one attributes

Question 16

If attribute B is functionally dependent on a composite key A but not any subset of A then B is _____ on A

Answer 16

Fully Functionally dependent

Question 17

Superkey

Answer 17

An attribute or a combination of attributes that uniquely identifies each row in a table

Question 18

Candidate Key

Answer 18

A minimal superkey, i.e., it does not contain a subset of attributes that is itself a superkey

Question 19

Primary Key

Answer 19

A candidate key selected to uniquely identify an entity
Cannot have null values
Enforces Entity Integrity
Is a superkey as well as a candidate

Question 20

Entity Integrity

Answer 20

Guarantees that each entity is uniquely identified by a non-null primary key value

Question 21

Foreign Key

Answer 21

An attribute (or a combination of attributes) in one table whose values must either match the primary key values in a designated table to be null
Used to logically link one table with another
Enforces Referential Integrity

Question 22

Referential Integrity

Answer 22

Guarantees valid references to another table, i.e., cannot delete a tuple from a table that is references by in another table through a foreign key

Question 23

Secondary Key

Answer 23

Used for data retrieval purpose
May consist of a single attribute or a combination of attributes
The DBMS maintains indexes on secondary keys for faster search and retrieval of data
May have duplicate values

Question 24

Relational Database Operators

Answer 24

Based on relational algebra theory
Define functions to manipulate data in one or more tables (relations)
Application of a relational operator to one or more tables results in another table

Question 25

Eight relational operators are:

Answer 25

UNION INTERSECT DIFFERENCE PRODUCT SELECT PROJECT JOIN DIVIDE

Question 26

Union Compatibility

Answer 26

Two table are said to be union-compatible when they have the same degree (number of attributes)

Question 27

Union

Answer 27

The tables must be union compatible A Union B results in C that contains all tuple from both A and B with no duplicates

Question 28

Intersect

Answer 28

The tables must be union compatible A Intersect B results in C that contains tuples that are common to both A and B

Question 29

Difference

Answer 29

The tables must be union compatible A MINUS B results in C that contains the tuples that appear in A but not in B

Question 30

Product

Answer 30

PRODUCT produces a list of all possible pairs of rows from two tables If table A has 5 rows and B has 10, A product B will yield a table with 50 rows

Question 31

Select

Answer 31

Yields all attributes of selected tuple that satisfy a specified condition Produces a horizontal subset of a table

Question 32

Project

Answer 32

Produces a list of all values for selected attributes It yields a vertical subset of a table

Question 33

Join

Answer 33

Allows us to combine information from two or more tables The tables participating in the join operation must have attributes defined over a common domain

Question 34

EquiJoin

Answer 34

Compares specified column of two tables based on equality condition

Question 35

Natural Join

Answer 35

EquiJoin with the duplicate column removed Performed by a Project on the result of equijoin (Inner Join)

Question 36

Natural Join

Answer 36

When the term Join is mentioned without any prefix

Question 37

Outer Join

Answer 37

Unmatched rows from the participating tables are retained in the result table with unmatched attributes left blank or null

Question 38

Left Outer join

Answer 38

Keeps all tuple from the left relation

Question 39

Right Outer Join

Answer 39

Keeps all tuple from the right section

Question 40

Theta Join

Answer 40

EquiJoin with the equality operator replaced by any other comparison operator, such as greater than, less than, etc

Question 41

Data Dictionary

Answer 41

Contains metadata that describes the data stored in the database

Question 42

Data Dictionary stores:

Answer 42

The names of the data items in the database Types and sizes of the data items Constraints on each data item Names of authorized users and types of access allowed

Question 43

System Catalog

Answer 43

Very detailed system data dictionary Describes all objects within the database

Question 44

System Catalog cont.

Answer 44

System-created database Tables can be queried just like any other tables Automatically produces database documentation All data dictionary information are found in here