SQL Optimization Techniques for Large Tables

SQL performance problems are very common in Indian IT companies like TCS, Infosys, Wipro, Accenture, and startups working with large databases. When tables grow to millions of rows, slow queries can crash applications.

This guide explains practical SQL optimization techniques every backend developer should know.

👉 Try SQL Generator Tool → https://dev-brains-ai.com/sql-generator

1️⃣ Use Indexing Properly

Indexes speed up search queries. Always index columns used in WHERE, JOIN, and ORDER BY.

CREATE INDEX idx_employee_salary
ON employees(salary);

Without index → full table scan With index → fast lookup

2️⃣ Avoid SELECT *

Fetch only required columns to reduce memory and network load.

-- Slow
SELECT * FROM employees;

-- Fast
SELECT name, salary FROM employees;

3️⃣ Use WHERE Clause Efficiently

-- Slow
SELECT * FROM employees
WHERE YEAR(join_date) = 2024;

-- Fast
SELECT * FROM employees
WHERE join_date >= '2024-01-01'
AND join_date < '2025-01-01';

Avoid functions on indexed columns.

4️⃣ Use LIMIT for Testing

SELECT * FROM logs
ORDER BY created_at DESC
LIMIT 100;

5️⃣ Optimize JOIN Queries

• Join indexed columns
• Reduce unnecessary joins
• Filter before join

SELECT o.id, c.name
FROM orders o
JOIN customers c
ON o.customer_id = c.id
WHERE o.date > '2024-01-01';

6️⃣ Use Table Partitioning

Partition big tables by date or region.

CREATE TABLE sales_2025 PARTITION OF sales
FOR VALUES FROM ('2025-01-01') TO ('2026-01-01');

7️⃣ Use Query EXPLAIN

EXPLAIN SELECT * FROM employees WHERE salary > 50000;

8️⃣ Real Optimization Examples in India

• GST invoice database optimization
• Petrol bunk sales reporting
• E-commerce order tracking
• Bank transaction monitoring
• IoT farming data storage

9️⃣ Common Mistakes Developers Make

• No indexes
• Too many joins
• Using SELECT *
• No query caching
• Large text columns in queries

👉 Use Dev-Brains-AI Error Explainer → https://dev-brains-ai.com/ai-error-explainer

Tips for Freshers Learning SQL Performance

• Practice with 1M+ rows dataset
• Learn indexing deeply
• Use EXPLAIN daily
• Understand database architecture

Conclusion

SQL optimization is a critical skill for backend developers. Learning indexing, query tuning, and partitioning will help you build scalable systems and crack interviews.

Practice using Dev-Brains-AI SQL tools to improve faster.

👉 https://dev-brains-ai.com/