Business Analyst: What is an index in SQL?

Index — data structure for faster queries.

Purpose:

• Speed up SELECT queries.
• Improve search performance.

Types:

• Primary key — unique identifier.
• Unique — no duplicates.
• Composite — multiple columns.
• Full-text — text search.

Example:

1-- Create index
2CREATE INDEX idx_customer_email
3ON customers (email);
4
5-- Composite index
6CREATE INDEX idx_order_date_status
7ON orders (order_date, status);

Trade-offs:

• Faster reads.
• Slower writes.
• Storage overhead.

BA relevance:

• Understand performance.
• Define search requirements.