Thilan Dissanayaka Database Systems Apr 26

Database Indexing: Speeding Up Your Queries Like a Pro

In the world of databases, speed matters. Whether you're powering an e-commerce store, a social media app, or a business dashboard — users expect data to load instantly. That’s where database indexing becomes your secret weapon.

Without indexes, the database has to scan every single row to find what it needs. That’s fine for tiny tables—but for millions of rows? You’ll feel the slowdown. Let’s explore how indexing works, the different types available, and how to use them wisely.

🔍 What is Database Indexing?

Think of a database index like the index in a book. Instead of flipping through every page to find a topic, you jump straight to the page number listed. A database index works the same way: it helps the database engine find rows faster without scanning the entire table.

⚙️ How Does an Index Work?

When you create an index on a column (or multiple columns), the database creates an internal structure — usually a B-tree or a hash table — that maps values in that column to the location of their corresponding rows.

So instead of scanning rows line by line, the database can go straight to the rows that match your query — dramatically improving speed.

Types of Database Indexes

  1. Primary Index

Automatically created when a primary key is defined.

Ensures unique identification of each record.

Left columns Right columns
left foo right foo
left bar right bar
left baz right baz

Example:

CREATE TABLE users (
    id INT PRIMARY KEY,
    name VARCHAR(100)
);
  1. Unique Index

Ensures that the indexed column values are unique.

Prevents duplicate entries.

Example:

CREATE UNIQUE INDEX idx_email ON users(email);
  1. Composite Index

Created on multiple columns to optimize queries involving those columns.

Example:

CREATE INDEX idx_name_age ON users(name, age);
  1. Full-Text Index

Designed for text-search capabilities.

Optimized for matching keywords in large text fields.

Example:

CREATE FULLTEXT INDEX idx_description ON products(description);
  1. Clustered Index

Sorts and stores rows based on the index key.

Each table can have only one clustered index.

Example:

CREATE CLUSTERED INDEX idx_order_id ON orders(order_id);
  1. Non-Clustered Index

Stores pointers to actual table rows.

A table can have multiple non-clustered indexes.

Example:

CREATE NONCLUSTERED INDEX idx_last_name ON employees(last_name);

Benefits of Indexing

Faster Query Execution: Reduces the need for full table scans.

Improved Sorting: Optimizes ORDER BY and GROUP BY operations.

Efficient Filtering: Speeds up WHERE clause evaluations.

Enhanced Join Performance: Accelerates JOIN operations between tables.

When to Use Indexes

On columns frequently used in search conditions (e.g., WHERE clauses).

For columns involved in sorting (e.g., ORDER BY).

In JOIN operations on foreign keys.

When to Avoid Indexes

On small tables where indexing overhead outweighs benefits.

For columns with low cardinality (few unique values).

On columns frequently updated, as indexes require maintenance.

Best Practices for Indexing

  • Use Selective Indexes: Prioritize columns with high cardinality.

  • Limit Composite Indexes: Avoid creating indexes with too many columns.

  • Monitor and Optimize: Regularly analyze index performance.

  • Index Strategically: Balance read performance with write overhead.

ALSO READ
How stack works in function call
Mar 23 Application Security

## The Stack in Computer Science The stack is an important concept in computer science. If you are planning to learn reverse engineering, malware analyzing, exploitation, etc., this concept is a....

Reverse TCP shell with Metasploit
Mar 23 Penetration Testing

Metasploit is a powerful penetration testing framework that automates exploit development, generates shellcode, and acts as a listener for incoming connections. This tutorial introduces how to create....

Adapter Pattern explained simply
Apr 26 Software Architecture

Ever needed to connect two incompatible interfaces without changing their source code? That’s exactly where the **Adapter Pattern** shines! The Adapter Pattern is a structural design pattern....

 OWASP Top 10 explained - 2021
Mar 03 Application Security

The Open Worldwide Application Security Project (OWASP) is a nonprofit foundation focused on improving the security of software. It provides free, vendor-neutral tools, resources, and standards that....

Building a Web3 CLI Tool for the Ballerina Language: From Idea to Reality
Apr 26 WSO2

🚀 Excited to finally share my journey of building a web3 CLI tool for Ballerina! This tool bridges the gap between Ethereum smart contracts and the Ballerina programming language by automatically....

ACID Properties in Databases: The Key to Reliable Transactions
Apr 25 Database Systems

When working with databases, one thing is absolutely critical: keeping your data safe, consistent, and reliable. That's where ACID properties come in — a set of principles that ensure every....