We'll respond shortly.
“Postgres SELECT * GROUP BY insists that all selected fields must either appear in the GROUP BY or be aggregated.”
Many agreed that this is, in fact, how a database should behave and that MySQL’s leniency on this matter is faulty. If you select a field that you don’t group by, you must tell Postgres how to combine the sub-set of values that fall in a given group into a single result (should it take the max? the min? the mean? the most purple?).