Have you optimized SQL queries to improve their efficiency?

Yes, SQL query optimization is an important step in improving application performance. I usually start by analyzing the execution plan (EXPLAIN) to understand which operations take the most time. I often optimize queries by:

• Adding or adjusting indexes on frequently used columns.
• Avoiding SELECT * and selecting only necessary fields.
• Rewriting complex JOINs or subqueries into more efficient constructs.
• Using aggregate functions and grouping only where necessary.

Example of optimization:

-- Was
SELECT * FROM orders o JOIN customers c ON o.customer_id = c.id WHERE c.status = 'active';

-- Optimized
SELECT o.id, o.date, c.name FROM orders o
JOIN customers c ON o.customer_id = c.id
WHERE c.status = 'active';

It is also important to monitor database statistics and regularly update them for the optimizer to work correctly.