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.

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 following SQL statement lists the number of customers in each country:

Example

SELECT COUNT(CustomerID), Country<br>FROM Customers<br>GROUP BY Country;

The following SQL statement lists the number of customers in each country, sorted high to low:

Example

SELECT COUNT(CustomerID), Country<br>FROM Customers<br>GROUP BY Country<br>ORDER BY COUNT(CustomerID) DESC;

Demo Database

Below is a selection from the “Orders” table in the Northwind sample database:

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 following SQL statement lists the number of orders sent by each shipper:

Example

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

MySQL GROUP BY Clause

The MYSQL GROUP BY Clause is used to collect data from multiple records and group the result by one or more column. It is generally used in a SELECT statement.

You can also use some aggregate functions like COUNT, SUM, MIN, MAX, AVG etc. on the grouped column.

Syntax:

SELECT expression1, expression2, ... expression_n,   
aggregate_function (expression)  
FROM tables  
[WHERE conditions]  
GROUP BY expression1, expression2, ... expression_n;  

Parameters

aggregate_function: It specifies a function such as SUM, COUNT, MIN, MAX, or AVG etc. tables: It specifies the tables, from where you want to retrieve the records. There must be at least one table listed in the FROM clause.

WHERE conditions: It is optional. It specifies the conditions that must be fulfilled for the records to be selected.

(i) MySQL GROUP BY Clause with COUNT function

Consider a table named “officers” table, having the following records.

Now, let’s count repetitive number of cities in the column address.

Execute the following query:

SELECT address, COUNT(*)  
FROM   officers   
GROUP BY address;   

Output:

(ii) MySQL GROUP BY Clause with SUM function

Let’s take a table “employees” table, having the following data.

Now, the following query will GROUP BY the example using the SUM function and return the emp_name and total working hours of each employee.

Execute the following query:

SELECT emp_name, SUM(working_hours) AS "Total working hours"  
FROM employees  
GROUP BY emp_name;

Output:

(iii) MySQL GROUP BY Clause with MIN function

The following example specifies the minimum working hours of the employees form the table “employees”.

Execute the following query:

SELECT emp_name, MIN(working_hours) AS "Minimum working hour"  
FROM employees  
GROUP BY emp_name;  

(iv) MySQL GROUP BY Clause with MAX function

The following example specifies the maximum working hours of the employees form the table “employees”.

Execute the following query:

SELECT emp_name, MAX (working_hours) AS "Minimum working hour"  
FROM employees  
GROUP BY emp_name; 

Output:

(v) MySQL GROUP BY Clause with AVG function

The following example specifies the average working hours of the employees form the table “employees”.

Execute the following query:

<strong>SELECT</strong> emp_name, AVG(working_hours) <strong>AS</strong> "Average working hour"  

FROM employees  

GROUP BY emp_name;  

Output:

: