At what level do you know SQL, what queries do you write?

I am proficient in SQL, capable of writing data retrieval queries (SELECT) with filtering, sorting, joins (JOIN), grouping (GROUP BY), as well as insert (INSERT), update (UPDATE), and delete (DELETE) queries.

I often write complex queries with subqueries, aggregate functions, and use indexes for optimization. I also know how to create and modify table structures (DDL), work with transactions, and understand query execution plans for performance analysis.