GROUB BY with more than one column

Question

I (who is not very good at SQL) was explaining GROUP BY clause in SQL to my beginner colleague . I showed him an example where results are grouped for one column . Something like
select customer, count(*) as ItemCount
from Orders
group by customerCould you guys give us a meanigful, simple and easy to remember example where two columns are being grouped

Answer 1

Hi Zebra,
Got this example from Google
DROP TABLE myenterprise;
CREATE TABLE myenterprise(
city VARCHAR2(10),
storeid VARCHAR2(10),
month_name VARCHAR2(10),
total_sales NUMBER);
INSERT INTO myenterprise(city, storeid, month_name, total_sales)
  VALUES ('paris', 'id1', 'January', 1000);
INSERT INTO myenterprise(city, storeid, month_name, total_sales)
  VALUES ('paris', 'id1', 'March', 7000);
INSERT INTO myenterprise(city, storeid, month_name, total_sales)
  VALUES ('paris', 'id1', 'April', 2000);
INSERT INTO myenterprise(city, storeid, month_name, total_sales)
  VALUES ('paris', 'id2', 'November', 2000);
INSERT INTO myenterprise(city, storeid, month_name, total_sales)
  VALUES ('paris', 'id3', 'January', 5000);
INSERT INTO myenterprise(city, storeid, month_name, total_sales)
  VALUES ('london', 'id4', 'Janaury', 3000);
INSERT INTO myenterprise(city, storeid, month_name, total_sales)
  VALUES ('london', 'id4', 'August', 6000);
INSERT INTO myenterprise(city, storeid, month_name, total_sales)
  VALUES ('london', 'id5', 'September', 500);
INSERT INTO myenterprise(city, storeid, month_name, total_sales)
  VALUES ('london', 'id5', 'November', 1000);
-- GROUPing of one column (which you already have)
SELECT city, SUM(total_sales) AS TOTAL_SALES_PER_CITY
FROM myenterprise
GROUP BY city
-- Two columns making up a group
select city, month_name, sum(total_sales) as total_sales_per_city
from myenterprise
group by city, month_name
order by total_sales_per_city desc;