Introduction
CTEs (Common Table Expressions) make SQL queries more readable and easier to manage.
What is a CTE?
A temporary result set defined within a query.
Syntax
WITH cte_name AS (
SELECT column_name FROM table_name
)
SELECT * FROM cte_name;
Example
WITH high_salary AS (
SELECT * FROM employees WHERE salary > 5000
)
SELECT * FROM high_salary;
Benefits of CTE
- Improves readability
- Simplifies complex queries
- Reusable logic
CTE vs Subquery
- CTE is more readable
- Easier to debug
- Better for complex queries
Common Mistakes
- Overusing CTEs
- Confusing scope
- Poor performance in large queries
Conclusion
CTEs are essential for writing clean and maintainable SQL queries.