Question 1

What is a database?

Accepted Answer

A collection of data items related to some enterprise.

Question 2

In the Relational Model, data is stored in

Accepted Answer

Tables

Question 3

The word "Relational" refers to __________, while a "Relation" is a __________.

Accepted Answer

set-based mathematics;  a table

Question 4

Physical data independence means

Accepted Answer

Data is isolated from the underlying hardware by high level abstractions.

Question 5

If a table contains two attributes that are each unique on their own, and either one could serve as a primary key, these attributes are called

Accepted Answer

Candidate keys

Question 6

Every table must have a

Accepted Answer

Primary Key

Question 7

Rows in a relational table need not be unique; there can be duplicate rows in a table

Accepted Answer

False

Question 8

"Tuple" is the mathematical name that is analogous to a

Accepted Answer

Row

Question 9

The mathematically-based framework of Codd's Relational Model is called a "__________ Data Model".

The data-structure-based framework of Bachman's Network Database is called a "__________ Data Model".

Accepted Answer

Conceptual, Physical

Question 10

Which of the following is not part of Peter Chen's Entity Relationship model?

Accepted Answer

Primary Keys

Question 11

In a one-to-many (1:M) relationship, the entity on the "many" side is the

Accepted Answer

child

Question 12

An ID-Dependent Entity is

Accepted Answer

An entity whose identifier (key) contains the identifier of another entity.

Question 13

"One-to-one", "one-to-many", and "many-to-many" (or 1:1, 1:M, and M:M) are examples of

Accepted Answer

cardinality ratios

Question 14

A table in a database is equivalent to a(n) _____ in an ER Diagram, and a row or tuple is equivalent to a(n) _____.

Accepted Answer

Entity Class, Entity Instance

Question 15

All ID-dependent entities are weak, but not all weak entities are ID-dependent

Accepted Answer

True

Question 16

An advantage in expressing a data model as an ER diagram is that ER diagrams are very uniform in their notation and all database designers use identical standards in producing ER diagrams.

Accepted Answer

False

Question 17

Mandatory Participation means

Accepted Answer

The minimum cardinality of a relationship is one or more

Question 18

A relationship name in an ER diagram can be different depending on the direction you read the relationship.

Accepted Answer

True

Question 19

We have to determine foreign keys when building an ER diagram.

Accepted Answer

False

Question 20

A Composite Identifier or Composite Key is

Accepted Answer

An Identifier or Key that is made up of more than one attribute.

Question 21

A mandatory participation constraint (meaning there is a required participation between one entity and another) always indicates that an entity is weak.

Accepted Answer

False

Question 22

In SQL, how do you select a column named "FirstName" from a table named "Employee"?

Accepted Answer

SELECT FirstName
FROM Employee

Question 23

In SQL, how do you select all the columns from a table named "Employee"?

Accepted Answer

SELECT * 
FROM Employee

Question 24

In SQL, how do you select all the rows from a table named "Employee" where the value of the column "FirstName" is "John"?

Accepted Answer

SELECT * 
FROM Employee 
WHERE FirstName = 'John'

Question 25

What SQL statement is used to return only different values from a table, eliminating duplicates?

Accepted Answer

SELECT DISTINCT

Question 26

With SQL, how can you return all the rows from a table named "Employee" sorted in descending order by FirstName?

Accepted Answer

SELECT * 
FROM Employee 
ORDER BY FirstName DESC

Question 27

In SQL, how do you list all the rows of the Employee table and Dependent table that match on the EmployeeId attribute?

Accepted Answer

SELECT * 
FROM Employee 
JOIN Dependent 
ON Employee.EmployeeId = Dependent.EmployeeId

Question 28

What query would we use to select all the employees from the Employee table whose first name is the same as his last name?

Accepted Answer

SELECT * 
FROM Employee 
WHERE FirstName = LastName

Question 29

What is the difference between an INNER JOIN and a LEFT JOIN? Remember that "JOIN" is the same as "INNER JOIN".

Accepted Answer

The INNER JOIN returns only the rows in which the join attributes match, and the LEFT JOIN returns all of the rows of the left table, along with the rows of the right table in which the join attributes match.

Question 30

In SQL, how do you add a new row to the table named 'Employee'?

Accepted Answer

INSERT INTO Employee (empNo, fName, lName)
VALUES (245, 'Bill', 'Jones');

Question 31

In SQL, how do you change the value of an attribute in an existing row?

Accepted Answer

UPDATE Employee 
SET DeptNum = 200 
WHERE EmpNum = 493;

Question 32

In SQL, how do you delete a row from a table?

Accepted Answer

DELETE 
FROM Employee 
WHERE EmpNum = 449;

Question 33

In DDL (Data Definition Language) you can do these three major types of tasks (among other things):

Accepted Answer

CREATE ALTER DROP

Question 34

The primary purpose of the Subtype/Supertype relationship is to

Accepted Answer

Eliminate type-inappropriate nulls

Question 35

To implement a Many-to-Many relationship in a relational database, you do this:

Accepted Answer

Add an intersection table between the two tables. The intersection table will contain a foreign key to each of the two tables being linked.

Question 36

The relational model does not directly support many-to-many relationships.

Accepted Answer

True

Question 37

The hallmark of an ID-dependent entity is that it

Accepted Answer

has the identifier (key) of another entity as part of its own identifier.

Question 38

The Association data pattern is similar to a ______ relationship, but with the addition of extra attributes in the ______ table which transforms it to an association table.

Accepted Answer

many-to-many, intersection

Question 39

Is a foreign key always the key of another table? (Answer True=Yes; False=No)

Accepted Answer

False

Question 40

If we want to record multiple e-mail addresses for each person in our Contact table, which data pattern would we use?

Accepted Answer

Multivalued attribute pattern

Question 41

Referential Integrity means:

Accepted Answer

assuring that the connections between tables remain valid

Question 42

Aggregate functions work with

Accepted Answer

groups of rows

Question 43

The WHERE clause filters _____ , while the HAVING clause filters _____ .

Accepted Answer

individual rows, groups

Question 44

WHERE and HAVING are similar because both are

Accepted Answer

filters

Question 45

A correlated subquery is executed each time

Accepted Answer

the outer query reads a row from a table

Question 46

If a SQL statement contains a GROUP BY clause, then the SELECT clause can contain only:

Accepted Answer

the GROUP BY attribute plus aggregate functions

Question 47

n a SQL query containing a GROUP BY clause, filtering of individual rows occurs before filtering and sorting of groups.

Accepted Answer

True

Question 48

A subquery can appear in a SQL statement wherever a _____ can appear.

Accepted Answer

table

Question 49

A correlated subquery can often be replaced by a

Accepted Answer

join

Question 50

Referential Integrity means

Accepted Answer

a foreign key value in a child table always has a matching primary key value in a parent table.

Question 51

a "Cascading Delete" is

Accepted Answer

Deleting a row in a parent table automatically deletes any corresponding rows linked by a foreign key in the child table, thereby preventing orphans.

Question 52

When a table has more than one attribute that could each serve as the table's primary
key (for example EmployeeNum and SSN), we call these __________ Keys.

Accepted Answer

Candidate

Question 53

Since we want to consistently use only one key for linking tables together, we select one of the table's candidate keys as the __________ Key.

Accepted Answer

Primary

Question 54

The primary key of the first table is placed within a second table to establish a means of linking rows in the two tables that belong together, is the __________ Key.

Accepted Answer

Foreign

Question 55

A Foreign Key column is not a key itself. Each row in the child table contains the
same value in its Foreign Key attribute as in the Primary Key attribute of its Parent row. As a result, rows in the two tables are linked together. This works because:

Accepted Answer

The rows in the two tables have a common value.

Question 56

Give a short explanation of the mechanism whereby a row of one table can be
linked to rows of another table.

Accepted Answer

The Primary Key of the parent table can be placed into
the child table as a Foreign Key.

Question 57

What is meant by the term "Weak Entity"? Give an example of a weak entity and tell
why it's weak. Why would the database designer need to know it's weak?

Accepted Answer

A "Weak Entity" is an entity that can't stand on its own but need the presence of another entity. For example, "Report Card" is a weak entity to Student.

Question 58

Your job is to produce a parts table for a lawn mower. The lawn mower has several
assemblies: the engine, the deck, and the handle. The engine is composed of the block and the carburetor....

Accepted Answer

One‐to‐Many Recursive pattern

Question 59

The Recursive Pattern can model a

Accepted Answer

All of the above
The 1:1 Recursive pattern can model a list in the same way that a linked list can.
The 1:M Recursive pattern can model a tree. 
The M:M Recursive pattern can model a network.

Question 60

Why is using surrogate keys usually considered a good practice?

Accepted Answer

A surrogate key doesn't represent a fact about an entity. It's a pure
linking construct. If a natural key were used in a table, the fact it represents may change. This would violate the unchangability of primary keys and weaken referential integrity.

Question 61

If we search for NULL values using this statement:

SELECT *
FROM SomeTable
WHERE SomeAttribute = NULL;

why won't it return any rows?

Accepted Answer

This statement never returns rows because the WHERE clause never evaluates to True. It always evaluates to Unknown because the NULL on the right side of the equal sign is Unknown.

COP4710 - Midterm 14

2014 Summer COP4710 Midterm

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