Education_Purpose

1. Index in Oracle An Index is a database object that improves the speed of data retrieval. It acts like a pointer to data in a table, allowing queries to be executed more efficiently. Purpose: Enhances query performance by reducing the amount of data scanned. Types of Indexes: B-Tree Index : Default index type, best for high-cardinality columns. Bitmap Index : Best for low-cardinality columns (e.g., gender). Unique Index : Ensures all values in the column(s) are unique. Example: Creating an index on the EMPLOYEE table for the LAST_NAME column:      CREATE INDEX idx_lastname ON EMPLOYEE(LAST_NAME); 2. View in Oracle A View is a virtual table based on a query that pulls data from one or more tables. It does not store data but provides a way to simplify complex queries. Purpose: Provides data security, abstraction, and simplifies queries. Types of Views: Simple View : Based on a single table without group functions. Complex View : Based on multiple tables with group...

1. Trivial and Non-Trivial Functional Dependencies Definition of Functional Dependency A functional dependency X \rightarrow Y X → Y exists when the value of attribute X X  determines the value of attribute Y Y . Trivial Dependency: A dependency X → Y X \rightarrow Y  is trivial if Y Y  is a subset of X X . Example: Consider a relation R ( A , B ) R(A, B) : A , B → A A, B \rightarrow A  is trivial because A A  is already part of the left-hand side. Non-Trivial Dependency: A dependency X → Y X \rightarrow Y  is non-trivial if Y Y  is not a subset of X X . Example: In a relation R ( A , B ) R(A, B) , A → B A \rightarrow B  is non-trivial because B B  is not part of A A . Significance: Trivial dependencies do not provide new information, whereas non-trivial dependencies are critical for normalization and reducing redundancy. 2. Non-Loss Decomposition and Functional Dependencies Non-Loss Decomposition A decomposition is non-loss if the original...