Podcast
Questions and Answers
What is the primary purpose of domain constraints in a relational model?
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?
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?
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?
What occurs if a primary key is null in a relational database?
What kind of integrity constraint allows a table to have additional columns with null values?
What kind of integrity constraint allows a table to have additional columns with null values?
Which of the following best explains the idea of a key constraint?
Which of the following best explains the idea of a key constraint?
How does a domain constraint affect the data type of an attribute?
How does a domain constraint affect the data type of an attribute?
When must referential integrity constraints be enforced?
When must referential integrity constraints be enforced?
What does the degree of a relation in the relational model represent?
What does the degree of a relation in the relational model represent?
Which of the following accurately describes a domain in the context of a relational database?
Which of the following accurately describes a domain in the context of a relational database?
What is a relation key in a relational database?
What is a relation key in a relational database?
In schema design, what is the primary purpose of normalization?
In schema design, what is the primary purpose of normalization?
Which integrity constraint ensures that a field contains only values from a specific domain?
Which integrity constraint ensures that a field contains only values from a specific domain?
What does the cardinality of a relation represent in a relational database?
What does the cardinality of a relation represent in a relational database?
What characteristic distinguishes a tuple in the relational model?
What characteristic distinguishes a tuple in the relational model?
In the context of relations, what is a schema?
In the context of relations, what is a schema?
What is the purpose of a primary key in an entity set?
What is the purpose of a primary key in an entity set?
Which statement accurately describes a trigger?
Which statement accurately describes a trigger?
What condition must be met for an assertion to be valid?
What condition must be met for an assertion to be valid?
In the syntax for creating a trigger, what does 'FOR EACH ROW' signify?
In the syntax for creating a trigger, what does 'FOR EACH ROW' signify?
What is an implication of allowing a primary key to contain a null value?
What is an implication of allowing a primary key to contain a null value?
Which of the following is NOT a valid action specified in a trigger?
Which of the following is NOT a valid action specified in a trigger?
How should assertions be treated when used in a database?
How should assertions be treated when used in a database?
What is a suitable use case for a trigger in a database?
What is a suitable use case for a trigger in a database?
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.
