ti chiedevo senza il comando GROUP che errore ti davaSELECT Data, SUM(Importo) FROM incassi WHERE n_macchina = 2 GROUP BY SUBSTRING(Data,4,2)\nExpression #1 of SELECT list is not in GROUP BY clause and contains nonaggregated column 'manzuoli14424.incassi.Data' which is not functionally dependent on columns in GROUP BY clause; this is incompatible with sql_mode=only_full_group_by