Return every compound carrying the GHS hazard code H225, "highly flammable liquid and vapor", with its name and formula. A hazard hangs off a listing, so the same compound can reach you through several entries — return each compound once. hazard_statements.system separates the vocabularies, and H225 lives in ghs-hazard. Seventeen compounds answer this.
A intermediate exercise, answered in SQL. It is marked by the rows your query returns rather than by how you wrote it, with 3 hints if you want them.
Ask the same question of a chemical dataset in SQL and in Mango and compare the two answers. The database is a SQLite file your browser downloads once and queries locally, so nothing you write ever leaves your machine — which is also why the tool needs JavaScript.