Relational Databases Overview

Relational Databases

• Relational databases store and access related data points.
• Data is organized into tables, each representing a specific entity.
• Each table has rows (records) and columns (fields).
• Tables are linked using relationships to enable complex queries and ensure data integrity.
• Columns/sets of columns in a table uniquely identifying each row are primary keys.
• Columns/sets of columns in one table pointing to rows in another table are foreign keys.

Why Relationships Matter

• Data integrity: ensures data accuracy and consistency.
• Prevents invalid data insertion (e.g., preventing order referencing a nonexistent customer).
• Efficient data retrieval: facilitates complex queries across multiple tables (e.g., finding customers and their orders).
• Reduced data redundancy: avoids data duplication by storing related data in separate tables (e.g., storing customer once, referencing in order details).

Entity Relationship Diagrams (ERDs)

• ER diagrams assist in identifying entities, their attributes, and relationships.
• Show different types of relationships: one-to-one, one-to-many, many-to-one, and many-to-many.

Steps for ER Model Creation

• Identify entities.
• Define relationships between entities.
• Determine attributes for each entity.
• Define keys (primary and foreign keys).
• Draw the diagram using standard symbols (rectangles, diamonds, ovals).

Normalization

• Organizes data efficiently to avoid redundancy and ensure data integrity.
• Eliminates data redundancy.
• Uses primary and foreign keys to link tables efficiently.
• Reduces transitive dependencies.

1st Normal Form

• Each column contains only atomic values (single words or numbers).

2nd Normal Form

• Eliminates partial dependencies, where non-key attributes depend on only part of the primary key.

3rd Normal Form

• Eliminates non-key attributes that depend on other non-key attributes.

Database Design

• Defines storage, retrieval, and mechanisms in database systems.
• Blueprint of how data is stored, accessed, and managed.
• Scheme definition: details tables, fields, data types, and relationships.
• Normalization ensures structure minimizes redundancy and maintains data integrity.
• Physical implementation details how the logical schema is stored and accessed.
• Performance optimization: enhances database speed through techniques like indexing, partitioning, and query optimization.

This quiz explores the fundamental concepts of relational databases, including how data is organized into tables, the significance of primary and foreign keys, and the importance of relationships in maintaining data integrity. Test your understanding of Entity Relationship Diagrams and their role in database design.