? MySQL INDEX

? Quick Overview

In MySQL, an index is a data structure that improves the speed of data retrieval operations on a table. Indexes help MySQL locate rows efficiently without scanning every record, similar to an index in a book.

? Key Concepts

PRIMARY KEY – Uniquely identifies rows and automatically creates an index.
UNIQUE INDEX – Ensures uniqueness across column values.
INDEX – Improves SELECT query performance.
FULLTEXT INDEX – Enables text-based searching.
SPATIAL INDEX – Optimizes spatial data queries.

⚙️ Syntax / Theory

? View Code Example

// Syntax for creating a MySQL index
CREATE INDEX index_name
ON table_name (column1, column2);

? Code Examples

? View Code Example

// Creating a composite index on employee names
CREATE INDEX idx_name
ON employees (last_name, first_name);

? View Code Example

// Dropping an existing index
DROP INDEX idx_name
ON employees;

? Live Output / Explanation

When an index exists on last_name, MySQL retrieves matching records significantly faster, especially for large datasets.

? Interactive Example

? View Code Example

// Using EXPLAIN to verify index usage
EXPLAIN
SELECT *
FROM employees
WHERE last_name = 'Doe';

? Use Cases

Optimizing search-heavy applications
Improving JOIN and ORDER BY performance
Enforcing data uniqueness
Accelerating reporting queries

✅ Tips & Best Practices

Create indexes on frequently queried columns.
Avoid excessive indexing to reduce write overhead.
Use EXPLAIN to validate index effectiveness.
Prefer composite indexes for multi-column filters.

? Try It Yourself

Create an index and compare query execution time.
Analyze index usage with EXPLAIN.
Implement a FULLTEXT index on a TEXT column.
Create and remove a UNIQUE index on an email field.