Rewrite a JOIN Query Without Using JOINs

Problem: Given a schema, write a query that answers a question both without using any JOIN, and again specifically using an INNER JOIN. Approach: The non-JOIN version typically uses a correlated subquery or a WHERE ... IN (SELECT ...) clause referencing the related table to achieve equivalent filtering logic. The INNER JOIN version explicitly joins the two tables on the shared key and filters/selects columns from the combined result set. Interviewer is testing whether the candidate understands that both approaches are logically equivalent for this type of filter, with JOINs generally being more efficient and readable for combining columns from multiple tables.