The most powerful SQL databases, like Oracle (but, in this case, also SQL Server, DB2 and Sybase) have a lot of tricks. This time we’re going to see one that applies to GROUP BY expressions. First, let’s define a simple schema: CREATE TABLE Sales ( country VARCHAR(10), sale_date DATE, amount NUMBER ); INSERT ALL INTO Sales VALUES ( 'Italy', TO_DATE('2014-10-01', 'YYYY-MM-DD'), 52) INTO Sales VALUES ( 'Italy', TO_DATE('2014-10-10', 'YYYY-MM-DD'), 54) INTO Sales VALUES ( 'Italy', TO_DATE('2...
