1
, ISYS 209 EXAM 3 NEWEST 2026 ACTUAL EXAM| ISYS
209 EXAM 3 REVIEW WITH COMPLETE REAL EXAM
QUESTIONS AND CORRECT VERIFIED ANSWERS/
ALREADY GRADED A+| (MOST RECENT!!)
Q1. In an entity-relationship (ER) diagram, which symbol
represents a relationship?
A) Circle
B) Rectangle
C) Diamond
D) Line
Correct Answer: C
Rationale: This is correct because in ER diagrams, relationships
(such as "enrolls in" or "works for") are represented by diamonds.
To clarify, entities are shown as rectangles, attributes as ovals or
circles, and lines connect entities to relationships. Thus, a diamond
is the proper symbol for a relationship.
Q2. Which of the following best defines a primary key?
A) A key that can contain null values
B) A key that uniquely identifies each record in a table
C) A key that references another table
D) A key made of multiple columns only
2
,Correct Answer: B
Rationale: This is correct because a primary key is a column (or
set of columns) that uniquely identifies each row in a table. In
other words, it guarantees that no two rows have the same
primary key value, and it cannot contain null values. Options A,
C, and D describe characteristics of foreign keys or composite
keys, not the primary key's defining function.
Q3. A foreign key is used to:
A) Speed up queries
B) Uniquely identify a row
C) Create a link between two tables
D) Store large binary data
Correct Answer: C
Rationale: This is correct because a foreign key in one table
references the primary key of another table, thereby
establishing a relationship between the two tables. For example,
an Orders table might have a CustomerID foreign key that links
to the Customers table. Options A, B, and D describe indexes,
primary keys, or BLOB storage, not the foreign key's purpose.
Q4. In an ER diagram, which cardinality means "one to
many"?
3
, A) 1:1
B) 1:N
C) M:N
D) 0:1
Correct Answer: B
Rationale: This is correct because 1:N (or 1 to many) means that
one entity instance relates to many instances of another entity.
For example, one customer can place many orders. In contrast,
1:1 means one-to-one, M:N means many-to-many, and 0:1 is not
a standard cardinality notation.
Q5. A composite key is:
A) A key that is also a foreign key
B) A key consisting of two or more columns
C) A key used for indexing only
D) A key that can be null
Correct Answer: B
Rationale: This is correct because a composite key (also called a
compound key) uses multiple columns together to uniquely
identify a row. For instance, in
a CourseRegistration table, (StudentID, CourseID) might together
form the composite primary key. Options A, C, and D are
4
, ISYS 209 EXAM 3 NEWEST 2026 ACTUAL EXAM| ISYS
209 EXAM 3 REVIEW WITH COMPLETE REAL EXAM
QUESTIONS AND CORRECT VERIFIED ANSWERS/
ALREADY GRADED A+| (MOST RECENT!!)
Q1. In an entity-relationship (ER) diagram, which symbol
represents a relationship?
A) Circle
B) Rectangle
C) Diamond
D) Line
Correct Answer: C
Rationale: This is correct because in ER diagrams, relationships
(such as "enrolls in" or "works for") are represented by diamonds.
To clarify, entities are shown as rectangles, attributes as ovals or
circles, and lines connect entities to relationships. Thus, a diamond
is the proper symbol for a relationship.
Q2. Which of the following best defines a primary key?
A) A key that can contain null values
B) A key that uniquely identifies each record in a table
C) A key that references another table
D) A key made of multiple columns only
2
,Correct Answer: B
Rationale: This is correct because a primary key is a column (or
set of columns) that uniquely identifies each row in a table. In
other words, it guarantees that no two rows have the same
primary key value, and it cannot contain null values. Options A,
C, and D describe characteristics of foreign keys or composite
keys, not the primary key's defining function.
Q3. A foreign key is used to:
A) Speed up queries
B) Uniquely identify a row
C) Create a link between two tables
D) Store large binary data
Correct Answer: C
Rationale: This is correct because a foreign key in one table
references the primary key of another table, thereby
establishing a relationship between the two tables. For example,
an Orders table might have a CustomerID foreign key that links
to the Customers table. Options A, B, and D describe indexes,
primary keys, or BLOB storage, not the foreign key's purpose.
Q4. In an ER diagram, which cardinality means "one to
many"?
3
, A) 1:1
B) 1:N
C) M:N
D) 0:1
Correct Answer: B
Rationale: This is correct because 1:N (or 1 to many) means that
one entity instance relates to many instances of another entity.
For example, one customer can place many orders. In contrast,
1:1 means one-to-one, M:N means many-to-many, and 0:1 is not
a standard cardinality notation.
Q5. A composite key is:
A) A key that is also a foreign key
B) A key consisting of two or more columns
C) A key used for indexing only
D) A key that can be null
Correct Answer: B
Rationale: This is correct because a composite key (also called a
compound key) uses multiple columns together to uniquely
identify a row. For instance, in
a CourseRegistration table, (StudentID, CourseID) might together
form the composite primary key. Options A, C, and D are
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