Unit 3 introduction to Oracle and Sql.pptx
- 1. INTRODUCTION TO ORACLE AND SQL UNIT-3 S. Vasuki, M.C.A., Assistant Professor, Department of Computer Science Sri Sarada Niketan College of Science for Women, Karur.
- 2. Database Keys: A Guide Database keys play a crucial role in organizing and managing data efficiently. Understanding the different types of keys is fundamental to effective database design and implementation.
- 3. Importance of Keys in Database Design 1 Data Integrity Keys ensure that data is accurate, consistent, and reliable, minimizing errors and inconsistencies. 2 Data Relationships Keys establish relationships between tables, allowing for efficient data retrieval and management. 3 Data Security Keys can be used to enforce access control and protect sensitive data from unauthorized access.
- 4. Definition of Primary Key Uniqueness A primary key uniquely identifies each row in a table, ensuring that each record is distinct. Non-Null Primary key values cannot be empty or null, guaranteeing the existence of a unique identifier. Data Integrity Primary keys maintain data integrity by preventing duplicates and ensuring data consistency across the database.
- 5. Definition of Foreign Key Relationship Link A foreign key acts as a link between two tables, establishing a relationship between their data. Data Integrity Foreign keys ensure data integrity by maintaining consistency between related tables and preventing data inconsistencies. Data Validation Foreign keys enforce data validation by ensuring that foreign key values exist in the referenced table.
- 6. Definition of Candidate Key Unique Identifier A candidate key is a column or set of columns that can uniquely identify each row in a table. Multiple Candidates A table can have multiple candidate keys, making it possible to choose a primary key based on different criteria. Data Integrity Candidate keys contribute to data integrity by ensuring that no two rows share the same values in the candidate key columns.
- 7. Definition of Composite Key Composite Key A primary key that consists of two or more columns combined. Uniqueness Together, the columns form a unique identifier for each row in the table. Data Integrity Enforces data integrity by ensuring that no two rows have the same combination of values in the composite key columns.
- 8. Definition of Super Key Includes Primary Key A super key is a set of attributes that can uniquely identify a tuple in a relation and includes the primary key. Data Redundancy Super keys are often larger than primary keys, potentially leading to data redundancy. Data Integrity Super keys contribute to data integrity by ensuring that every attribute in the key is unique within the table.
- 9. Implementing Keys on Database Tables 1 Design Phase Identify and define primary and foreign keys during the database design process, ensuring data integrity from the outset. 2 Data Validation Implement data validation rules to ensure that primary and foreign keys are correctly entered and updated. 3 Data Relationships Establish relationships between tables using foreign keys, ensuring data consistency and integrity across the database.
- 10. SQL Commands for Creating and Managing Keys CREATE TABLE Students ( StudentID INT PRIMARY KEY, FirstName VARCHAR(255), LastName VARCHAR(255), Major VARCHAR(255) ); CREATE TABLE Courses ( CourseID INT PRIMARY KEY, CourseName VARCHAR(255), Department VARCHAR(255) ); CREATE TABLE Enrollments ( EnrollmentID INT PRIMARY KEY, StudentID INT, CourseID INT, FOREIGN KEY (StudentID) REFERENCES Students(StudentID), FOREIGN KEY (CourseID) REFERENCES Courses(CourseID) );
- 11. Best Practices for Using Keys Effectively 1 Choose Appropriate Keys Select keys that are truly unique and relevant to the data being stored. 2 Data Integrity Ensure that data integrity rules are enforced to prevent invalid key values and maintain data consistency. 3 Performance Optimization Optimize key usage to minimize data redundancy and improve database performance.