Create an aggregate table grouped by col showing meas
        The meas is something like "sum(in)" or "count(*)"
        RETURNS:
            DROP TABLE C_AGG_PRODUCT;
            CREATE TABLE C_AGG_PRODUCT AS (
                SELECT PRODUCT, sum(AMOUNT) AS result 
                FROM C_SALES GROUP BY PRODUCT
            );

def aggregate(self, opTable, group_by_cols, meas):
        """ 
        Create an aggregate table grouped by col showing meas
        The meas is something like "sum(in)" or "count(*)"
        RETURNS:
            DROP TABLE C_AGG_PRODUCT;
            CREATE TABLE C_AGG_PRODUCT AS (
                SELECT PRODUCT, sum(AMOUNT) AS result 
                FROM C_SALES GROUP BY PRODUCT
            );

        """
        self.sql_text += "DROP TABLE " + opTable + ";\n"
        self.sql_text += "CREATE TABLE " + opTable + " AS (\n"
        self.sql_text += "    SELECT " + group_by_cols + ", " + meas + " AS result \n"
        self.sql_text += "    FROM " + self.fact_table + " GROUP BY " + group_by_cols + "\n"
        self.sql_text += ");\n"