The cases are randomly generated; It asks for unique values of a random column in a random table. Sometimes it asks for unique password hashes... It's an edge case I didn't account for.
For replay-ability.
Each time you need to understand the problem and construct a query instead of remembering that the answer was X (when I prototyped this in some of the cases you needed to pick the right answer from a cell in the table, not submit the whole thing).