Introduction to SQL Indexes

Types of SQL Indexes

There are several types of indexes, each suited for different scenarios.

• B-Tree Indexes: The most common type, ideal for equality and range queries.
• Hash Indexes: Efficient for equality comparisons but not for range queries.
• Bitmap Indexes: Useful for columns with low cardinality (few distinct values).
• Unique Indexes: Ensure that indexed columns contain unique values.

How Indexes Improve Performance

Indexes allow the database to quickly locate data without scanning every row in a table.

By using an index, the database engine can jump directly to the relevant data pages.

• Speeds up SELECT queries with WHERE clauses.
• Improves JOIN operation efficiency.
• Enhances ORDER BY and GROUP BY performance.

Trade-offs and Considerations

While indexes improve read performance, they come with trade-offs.

Every time data is inserted, updated, or deleted, indexes must be maintained, which can slow down write operations.

• Indexes consume additional disk space.
• Too many indexes can degrade write performance.
• Choosing the right columns to index is critical for balancing read and write efficiency.