Lec-8.0: Integrity Constraints in Database with Examples
Understanding Integrity Constraints in Databases
Introduction to Integrity Constraints
- The video discusses integrity constraints in databases, emphasizing the importance of organizing data properly within tables.
- It highlights that data should not be inserted randomly; instead, rules must govern how data is entered to maintain its integrity.
Importance of Data Uniqueness
- The concept of uniqueness is introduced, stressing that values for attributes (like 'X') must not conflict across entries.
- Integrity constraints are defined as a set of rules that ensure accuracy and consistency in the database.
Types of Integrity Constraints
Domain Constraints
- Domain constraints relate to attributes within tables, ensuring that only valid data types are entered (e.g., integers for age).
- When creating attributes, specifying data types helps prevent invalid entries from being made.
Example of Domain Violation
- An example illustrates how entering an invalid value (like -5 for age) violates domain constraints.
- Implementing check constraints can prevent such violations by enforcing rules on acceptable values.
Primary Key and Its Role
Definition and Characteristics
- The primary key constraint ensures at least one attribute is unique and cannot be null in a table.
- A primary key guarantees no duplicate or null values exist, maintaining the integrity of the dataset.
Referential Integrity Constraint
Relationship Between Tables
- Referential integrity involves relationships between parent and child tables; child records must correspond to existing parent records.
- Violating this principle leads to inconsistencies where child records reference non-existent parent records.
Unique Constraints
Ensuring Uniqueness Across Attributes
- Unique constraints require at least one attribute in a table to be unique among all entries.
Understanding Candidate Keys and Their Properties
What is a Unique Candidate Key?
- A unique candidate key is fundamentally related to the properties of a candidate. It signifies that multiple keys can exist, but each must be unique in its context.
- The discussion emphasizes the importance of understanding what constitutes a candidate key, particularly focusing on its uniqueness as a property tied to candidates.
Importance of Primary and Foreign Keys
- The lecture highlights the distinction between primary keys and foreign keys, which are crucial concepts in database management.
- It is noted that these topics were previously covered in lectures 9 (Primary Key) and 10 (Foreign Key), indicating their foundational role in understanding data integrity.