Database Integrity Constraints Quiz

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Questions and Answers

What is the primary purpose of domain constraints in a relational model?

To allow null values in attributes

To define a valid set of values for an attribute (correct)

To enforce uniqueness of primary keys

To create relationships between tables

Which of the following correctly describes a primary key in a relational table?

It can be duplicated across rows.

It is optional for the table structure.

It can accept null values.

It must uniquely identify rows in the table. (correct)

Which type of constraint ensures that a foreign key in one table corresponds to a primary key in another table?

Domain constraint

Key constraint

Entity integrity constraint

Referential integrity constraint (correct)

What occurs if a primary key is null in a relational database?

The row cannot be uniquely identified. Signup and view all the answers

What kind of integrity constraint allows a table to have additional columns with null values?

Entity integrity constraint Signup and view all the answers

Which of the following best explains the idea of a key constraint?

It mandates the uniqueness of values in specific attributes. Signup and view all the answers

How does a domain constraint affect the data type of an attribute?

It specifies the allowable data types for the attribute. Signup and view all the answers

When must referential integrity constraints be enforced?

When relations between two tables exist. Signup and view all the answers

What does the degree of a relation in the relational model represent?

The total number of attributes in the relation Signup and view all the answers

Which of the following accurately describes a domain in the context of a relational database?

A domain specifies a set of valid values for an attribute Signup and view all the answers

What is a relation key in a relational database?

A combination of one or more attributes that uniquely identifies a tuple Signup and view all the answers

In schema design, what is the primary purpose of normalization?

To eliminate redundancy and ensure data integrity Signup and view all the answers

Which integrity constraint ensures that a field contains only values from a specific domain?

Domain integrity constraint Signup and view all the answers

What does the cardinality of a relation represent in a relational database?

The number of tuples in the relation Signup and view all the answers

What characteristic distinguishes a tuple in the relational model?

It represents a single record or row in a table Signup and view all the answers

In the context of relations, what is a schema?

The structure that defines the attributes and their data types for a relation Signup and view all the answers

What is the purpose of a primary key in an entity set?

To uniquely identify each record in the table. Signup and view all the answers

Which statement accurately describes a trigger?

A trigger is automatically executed in response to specific events. Signup and view all the answers

What condition must be met for an assertion to be valid?

It must always return true after any database modification. Signup and view all the answers

In the syntax for creating a trigger, what does 'FOR EACH ROW' signify?

The trigger operates at the row level for specific operations. Signup and view all the answers

What is an implication of allowing a primary key to contain a null value?

It can lead to data inconsistency across multiple tables. Signup and view all the answers

Which of the following is NOT a valid action specified in a trigger?

Deleting an existing column. Signup and view all the answers

How should assertions be treated when used in a database?

They must be used cautiously due to their strict enforcement. Signup and view all the answers

What is a suitable use case for a trigger in a database?

To automatically recalculate values upon updating a record. Signup and view all the answers

Study Notes

Attribute Domain

An Attribute Domain defines the possible values an attribute can hold.
It specifies a specific range of values.
It helps ensure data accuracy by controlling acceptable inputs.

Relational Integrity Constraints

Enforce data accuracy and accessibility by defining rules.
Constraints are checked before database operations (insert, delete, update).

Types of Constraints

Domain Constraint: Ensures attribute values are within a predefined range.
Key Constraint: Requires each relation to have a Primary Key – an attribute or set of attributes uniquely identifying tuples.
- The Primary Key cannot be NULL.
- It cannot have the same value for different tuples.
Referential Integrity Constraint: Defines a relationship between two tables.
- If a foreign key in Table 1 refers to the Primary Key of Table 2, the foreign key value in Table 1 must either be NULL or match a value in Table 2.

Entity Integrity Constraint

The Primary Key cannot be null.
It allows other attributes to hold null values.

Keys

Uniquely identify entities within a relation.

Relational Model Concepts

Schema: Defines the relation's name and its attributes.
- Example: CUSTOMER (Cust-id, Cust-name, Address, Phone#)
Domain: A logical definition of the valid values for an attribute.
- May have a data type or specific format.
- Example: USA_phone_numbers (format: (ddd)-ddd-dddd)
Relational Model (RM): Represents a database as a collection of relations (tables).
Attributes: Columns in a table, representing properties of a relation.
Tables: Store relations in a table format, with rows representing records and columns representing attributes.
Tuple: A single row in a table, containing a single record.
Relation Schema: Describes the name of the relation and its attributes.
Degree: The number of attributes in a relation.
Cardinality: The total number of rows (tuples) in a table.
Column: Holds values for a specific attribute in the table.
Relation Instance: A finite set of tuples at a specific point in time.
Relation Key: An attribute or set of attributes that uniquely identifies each tuple in a relation.

Trigger

A stored procedure (program) that automatically executes when a specific database event occurs.
Events: Insert, update, or delete operations on a table.
Used to enforce data integrity, manage complex business rules, track changes, or audit actions.

Assertion

A predicate (condition) that the database must always satisfy.
Checked after any change that could potentially violate the assertion.
Should be used carefully as they impact database performance if they are complex or frequent.

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Description

Test your knowledge on database integrity constraints, including attribute domains, relational integrity, and various types of constraints such as domain, key, and referential integrity. This quiz covers essential rules that ensure data accuracy and proper relationships between tables.