Return one row per IR spectrum with its compound, its source id, how many bands the supplier reported and how many this build picked, keeping only the spectra where picking found more. ir_peaks.source is reported or picked, and both live in the same table. Count each kind inside one grouping rather than joining the table to itself. Thirty-five spectra answer this; Nerol has twelve picked bands and no reported ones.
A advanced 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.