SQL GROUP BY detailed explanation and simple example

The GROUP BY statement is used in conjunction with the Aggregate function to group the result set based on one or more columns.

SQL GROUP BY Syntax

SELECT column_name, aggregate_function(column_name)
FROM table_name
WHERE column_name operator value
GROUP BY column_name;

Demo Database

In this tutorial, we will use the well-known Northwind sample database.

Here is the data selected from the "Orders" table:

Data from the "Shippers" table:

Data selected from the "Employees" table:

SQL GROUP BY Example

Now we want to find the number of orders delivered by each delivery person.

The following SQL statement classifies and counts orders by delivery person:

SELECT Shippers.ShipperName,COUNT(Orders.OrderID) AS NumberOfOrders FROM Orders
LEFT JOIN Shippers
ON Orders.ShipperID=Shippers.ShipperID
GROUP BY ShipperName;

GROUP BY more than one column

We can also apply GROUP BY clause to more than one column as shown below:

SELECT Shippers.ShipperName, Employees.LastName,
COUNT(Orders.OrderID) AS NumberOfOrders
FROM ((Orders
INNER JOIN Shippers
ON Orders.ShipperID = Shippers.ShipperID)
INNER JOIN Employees
ON Orders.EmployeeID = Employees.EmployeeID)
GROUP BY ShipperName,LastName;

Thank you for reading, I hope it can help you, thank you for your support of this site!