What is a fully NULL foreign key?

B) A foreign key with all columns set to NULL.

In the context of composite primary keys and foreign keys, what is a valid requirement?

B) foreign key referring to a composite primary key must also be composite.

What is a limitation of using SET NULL in the ON UPDATE or ON DELETE clauses for a foreign key?

B) It cannot be used when a foreign key is not allowed NULL values.

What is the purpose of a FOREIGN KEY constraint in a database?

C) It ensures referential integrity between tables.

Which operation does NOT violate referential integrity?

D) Performing primary key inserts

What does an empty circle (○) preceding a column indicate in a table diagram?

c) It indicates the column is a foreign key

What does the SET DEFAULT referential integrity action do?

B) It sets invalid foreign keys to the foreign key default value.

What are the four possible actions specified in the ON UPDATE and ON DELETE clauses for primary key updates and deletes?

B) RESTRICT, SET NULL, SET DEFAULT, CASCADE

How can referential integrity be compromised when working with primary keys?

A) Deleting a row with a primary key

What must be done when referential integrity violations occur in a relational database?

C) Violations must be corrected before data is stored in the database.

What action is taken by the RESTRICT referential integrity action?

B) rejects insert, update, or delete that violates referential integrity.

When multiple foreign keys refer to a P-key, can different actions be used for each F-key during updates or deletes?

B) Yes, different actions can be specified for each foreign key.

In terms of data types, what requirement must be met between foreign and primary keys?

b) They must have the same data type

When does the CASCADE referential integrity action apply?

A) It applies to primary key updates and deletes.

What is the purpose of a foreign key in a relational database?

b) To establish a link between two tables

Which of the following statements about foreign keys is true?

B) A foreign key may refer to a primary key in the same table.

How do foreign keys differ from primary keys?

b) Foreign keys may have NULL values, while primary keys cannot

Why is referential integrity crucial in a relational database?

C) prevents data entry errors and incomplete data by enforcing consistency.

What is the Referential Integrity Rule in a relational database?

B) ensures foreign key values are fully NULL or match a primary key value.

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sql quiz 2.10 - 2.11

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Answers

1
What is a fully NULL foreign key?
D) A foreign key with unique constraints.
B) A foreign key with all columns set to NULL.
A) A foreign key with no constraints.
C) A foreign key that references multiple primary keys.
2
What relational rule does a foreign key adhere to?
b) Referential integrity
a) Uniqueness constraint
c) Primary key constraint
d) Data normalization rule
3
In the context of composite primary keys and foreign keys, what is a valid requirement?
B) foreign key referring to a composite primary key must also be composite.
C) composite F-key has columns that dont match the primary key columns.
A) A foreign key referring to a composite primary key must always be NULL.
D) A composite foreign key can only refer to a single primary key column.
4
What is a limitation of using SET NULL in the ON UPDATE or ON DELETE clauses for a foreign key?
B) It cannot be used when a foreign key is not allowed NULL values.
A) It is not supported in MySQL.
D) SET NULL is always the default action.
C) It is only applicable to primary key updates.
5
What is the purpose of a FOREIGN KEY constraint in a database?
B) It specifies the data type of a column.
D) It allows NULL values in a column.
C) It ensures referential integrity between tables.
A) It enforces unique constraints on a column.
6
Which operation does NOT violate referential integrity?
A) Deleting a row with a foreign key
C) Updating a primary key
D) Performing primary key inserts
B) Inserting a row with a foreign key
7
What does an empty circle (○) preceding a column indicate in a table diagram?
c) It indicates the column is a foreign key
b) It represents a unique constraint on the column
a) It signifies the column is a primary key
d) It has no specific meaning in a table diagram
8
What does the SET DEFAULT referential integrity action do?
D) It propagates primary key changes to foreign keys.
C) rejects insert, update, or delete that violates referential integrity.
B) It sets invalid foreign keys to the foreign key default value.
A) It sets invalid foreign keys to NULL.
9
What are the four possible actions specified in the ON UPDATE and ON DELETE clauses for primary key updates and deletes?
A) REMOVE, MODIFY, ADD, DROP
C) DELETE, UPDATE, INSERT, SELECT
D) REFUSE, ACCEPT, IGNORE, ACKNOWLEDGE
B) RESTRICT, SET NULL, SET DEFAULT, CASCADE
10
How can referential integrity be compromised when working with primary keys?
D) Performing primary key inserts
C) Inserting a row with a foreign key
A) Deleting a row with a primary key
B) Updating a foreign key
11
What must be done when referential integrity violations occur in a relational database?
D) Violations only need correction if they involve primary key columns.
B) Violations are automatically corrected by the database system.
C) Violations must be corrected before data is stored in the database.
A) Violations can be ignored, as they do not affect database functionality.
12
Which referential integrity action sets invalid foreign keys to NULL?
B) SET NULL
C) SET DEFAULT
A) RESTRICT
D) CASCADE
13
What action is taken by the RESTRICT referential integrity action?
A) It sets invalid foreign keys to NULL.
D) It sets invalid foreign keys to the foreign key default value.
C) It propagates primary key changes to foreign keys.
B) rejects insert, update, or delete that violates referential integrity.
14
What action can potentially lead to a referential integrity violation?
B) Inserting a row with a foreign key
D) Updating a foreign key
A) Deleting a row with a primary key
C) Performing primary key inserts
15
In which scenario can referential integrity be violated?
D) Updating a primary key
C) Updating a foreign key
A) Primary key inserts
B) Foreign key deletes
16
When multiple foreign keys refer to a P-key, can different actions be used for each F-key during updates or deletes?
B) Yes, different actions can be specified for each foreign key.
A) No, the same action must be applied to all foreign keys.
C) Only RESTRICT can be applied to multiple foreign keys.
D) Actions are not allowed on multiple foreign keys.
17
In terms of data types, what requirement must be met between foreign and primary keys?
d) Data types of primary keys can be NULL
a) They must have different data types
c) Data types of foreign keys are not relevant
b) They must have the same data type
18
What action does MySQL automatically apply for foreign key inserts and updates when referential integrity is violated?
D) RESTRICT
A) SET NULL
C) CASCADE
B) SET DEFAULT
19
When does the CASCADE referential integrity action apply?
C) It applies to foreign key inserts and updates.
B) It applies to primary key updates only.
A) It applies to primary key updates and deletes.
D) It applies to primary key deletes only.
20
What is the purpose of a foreign key in a relational database?
a) To uniquely identify each record in a table
b) To establish a link between two tables
c) To perform mathematical operations on data
d) To define the primary key of a table
21
Which of the following statements about foreign keys is true?
D) A foreign key can have NULL values.
C) A foreign key must always be composite.
A) A foreign key can only refer to a primary key in a different table.
B) A foreign key may refer to a primary key in the same table.
22
How do foreign keys differ from primary keys?
d) Foreign keys are not involved in referential integrity
a) Foreign keys are unique, while primary keys may have duplicate values
b) Foreign keys may have NULL values, while primary keys cannot
c) Foreign keys are numeric, while primary keys can have various data types
23
Why is referential integrity crucial in a relational database?
D) It permits foreign keys to have mismatched values with primary keys.
B) It ensures that every column in a table has a unique value.
A) It allows for flexible data entry with minimal constraints.
C) prevents data entry errors and incomplete data by enforcing consistency.
24
What is the Referential Integrity Rule in a relational database?
B) ensures foreign key values are fully NULL or match a primary key value.
C) It allows foreign keys to have any value, whether NULL or not.
D) It restricts the use of NULL values in primary key columns.
A) It enforces unique constraints on primary key columns.

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