MySQL GROUP BY
The MySQL GROUP BY Statement
Rows with identical values are grouped together into summary rows using the GROUP BY command, as in “find the number of customers in each country”.
To group the result-set by one or more columns, the GROUP BY statement is frequently used in conjunction with aggregate functions (COUNT(), MAX(), MIN(), SUM(), AVG()).
GROUP BY Syntax
SELECT column_name(s)
FROM table_name
WHERE condition
GROUP BY column_name(s)
ORDER BY column_name(s);
Demo Database
Below is a selection from the “Customers” table in the Northwind sample database:
| CustomerID | CustomerName | ContactName | Address | City | PostalCode | Country |
|---|---|---|---|---|---|---|
| 1 | Alfreds Futterkiste | Maria Anders | Obere Str. 57 | Berlin | 12209 | Germany |
| 2 | Ana Trujillo Emparedados y helados | Ana Trujillo | Avda. de la Constitución 2222 | México D.F. | 05021 | Mexico |
| 3 | Antonio Moreno Taquería | Antonio Moreno | Mataderos 2312 | México D.F. | 05023 | Mexico |
| 4 | Around the Horn | Thomas Hardy | 120 Hanover Sq. | London | WA1 1DP | UK |
| 5 | Berglunds snabbköp | Christina Berglund | Berguvsvägen 8 | Luleå | S-958 22 | Sweden |
MySQL GROUP BY Examples
The quantity of clients in every nation is listed in the SQL statement that follows:
Example
SELECT COUNT(CustomerID), Country
FROM Customers
GROUP BY Country;
The following SQL statement lists the number of customers in each country, sorted high to low:
Example
SELECT COUNT(CustomerID), Country
FROM Customers
GROUP BY Country
ORDER BY COUNT(CustomerID) DESC;
Demo Database
A sample from the “Orders” table in the Northwind sample database is shown below:
| OrderID | CustomerID | EmployeeID | OrderDate | ShipperID |
|---|---|---|---|---|
| 10248 | 90 | 5 | 1996-07-04 | 3 |
| 10249 | 81 | 6 | 1996-07-05 | 1 |
| 10250 | 34 | 4 | 1996-07-08 | 2 |
And a selection from the “Shippers” table:
| ShipperID | ShipperName |
|---|---|
| 1 | Speedy Express |
| 2 | United Package |
| 3 | Federal Shipping |
GROUP BY With JOIN Example
The amount of orders that each shipper has sent is listed in the SQL statement that follows:
Example
SELECT Shippers.ShipperName, COUNT(Orders.OrderID) AS NumberOfOrders FROM Orders
LEFT JOIN Shippers ON Orders.ShipperID = Shippers.ShipperID
GROUP BY ShipperName;
