Assess your level of SQL knowledge.

My SQL knowledge level is intermediate (middle). I am confident in working with basic operators like SELECT, JOIN, GROUP BY, HAVING, and can write subqueries and use window functions. I am familiar with query optimization, indexes, and understand how to read execution plans.

Example of a query using a window function:

SELECT employee_id, department_id, salary,
       RANK() OVER (PARTITION BY department_id ORDER BY salary DESC) as salary_rank
FROM employees;

This allows ranking employees by salary within each department.