The GROUP BY statement groups rows that have the same values into summary rows, like "find the number of customers in each country".
The GROUP BY statement is often used with aggregate functions COUNT(), MAX(), MIN(), SUM(), AVG() to group the result-set by one or more columns.
Below is a selection from the "Customers" table in the Northwind sample database:
The following SQL statement lists the number of customers in each country:
The following SQL statement lists the number of customers in each country, sorted high to low:
Below is a selection from the "Orders" table in the Northwind sample database:
And a selection from the "Shippers" table:
The following SQL statement lists the number of orders sent by each shipper: