How well do you understand SQL queries and their usage?

I am well-versed in SQL queries and can use them effectively for working with databases. I know the basic commands: SELECT, INSERT, UPDATE, DELETE, and I can also construct complex queries with JOIN, GROUP BY, HAVING, and subqueries. For example, to select users with a specific status and sort by registration date, you can write:

SELECT id, username, email
FROM users
WHERE status = 'active'
ORDER BY registration_date DESC;

I am also familiar with query optimization and using indexes to improve performance.