A junior interview often starts with a small query and a follow-up about what its rows mean. Name the source grain before writing SQL. An order has one customer and can contain several items, while a customer can have no orders. Those relationships determine which counts and joins answer the question.
These original prompts alternate executable work with design choices. The queries are checked on different source data, so a memorized number won't pass. Read the requested aliases and output grain; a correct value in an ambiguous column is harder for another analyst to use. In the scenario questions, each wrong option names a common misconception, such as treating LIMIT as a scan control or comparing a missing value with equality. You can use the hints during practice, then repeat the set without them to rehearse an explanation.