I am using SQL. I don't understand subqueries at all. Question is the first image.

(Use the "my guitar shop" database to answer this question.) Write a SELECT statement that returns the category name column from the Categories table. Return one row for each category that has never been assigned to any product in the Products table. Use a subquery introduced with the NOTEXISTS operator. This is the result set you should get: Result Grid category name eyboards (1 row)