Whether you're building dashboards, optimizing APIs, or wrangling legacy data, knowing the basics of SQL is just the beginning. To write clean, efficient, and powerful queries, you need to go beyond SELECT *. In this post, we’ll explore five advanced SQL techniques that can seriously elevate your querying game — making your code cleaner, faster, and more scalable.

At Wakapi, we believe that better visibility into your coding habits leads to better development decisions, and writing smarter SQL is a key part of that journey.

1. Common Table Expressions (CTEs)

CTEs let you define temporary result sets that can be referenced within a SELECT, INSERT, UPDATE, or DELETE statement. Think of them as named subqueries that improve readability and make complex logic easier to manage.

Use CTEs to:

• Break complex queries into logical, readable parts
• Improve maintainability and debugging
• Avoid repeating subqueries across your code

2. Window Functions Window functions perform calculations across a set of rows related to the current row — without collapsing them into a single result. They’re essential for analytics and reporting.

3. CASE Statements

CASE is SQL’s built-in conditional logic — like if/else in other languages. It’s powerful for transforming data on the fly or creating derived columns.

SELECT name, salary, CASE WHEN salary > 100000 THEN 'High' WHEN salary > 50000 THEN 'Medium' ELSE 'Low' END AS salary_band FROM employees;

Use it to:

• Classify or bucket values
• Replace conditional logic in application code
• Simplify complex WHERE clauses

Use it to:

• Classify or bucket values
• Replace conditional logic in application code
• Simplify complex WHERE clauses

4. EXISTS vs. IN

Many developers default to IN for subqueries, but EXISTS can be significantly more efficient — especially with large datasets or correlated subqueries.

Choose EXISTS when:

• Working with large or correlated subqueries
• You need a boolean existence check
• Query performance is critical

5. Index-Aware Querying

Even well-written SQL can perform poorly if it doesn’t align with how your database stores and indexes data. Writing index-friendly queries is essential for performance.

Best practices:

• Avoid SELECT * — fetch only the columns you need
• Filter and join on indexed columns
• Avoid wrapping indexed columns in functions (e.g., LOWER(column_name))

Pro tip: Use EXPLAIN (PostgreSQL, MySQL) to analyze query plans and spot bottlenecks.

Final Thoughts These five techniques are just the beginning. Great SQL comes from a deep understanding of your data, your use case, and your database’s behavior. Mastering these patterns will help you write queries that are not only correct: but elegant, efficient, and scalable.

At Wakapi, we help our clients match with specialized devs so you can build smarter, faster, and better. Schedule a Meeting with our business development team and let´s start coding your next big project.