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Using SQL GROUP BY with Aggregate Functions

Reading time 2 min
Published Aug 9, 2017
Updated Oct 11, 2019

SQL GROUP BY Statement: Main Tips

  • The GROUP BY statement is used with aggregate functions (MAX, MIN, COUNT, AVG, SUM) to group the result-set by one or more columns.

Syntax of SQL GROUP BY

Groups the result-set by one or more columns

Example
SELECT mycolumn_name(s)
FROM mytable_name
WHERE condition
GROUP BY mycolumn_name(s)
ORDER BY mycolumn_name(s);
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Demo Database

This is demo example from the "Developers" table in the database:

ID Name City Country
1 Tom Kurkutis New York USA
2 Ana Fernandez London UK
3 Antonio Indigo Paris France
4 Aarav Kaelin Delhi India
5 Andrew Tumota Miami USA

And the demo example from the "Clients" table in the database:

ID Name Contact Address City Postal_Code Country
1 Ben Choplinks Ben Choplink Obeesre Str. 51 Rome 11207 Italy
2 Donald Rich Donald Richario Avda. de la Confgfstitución 4122 Tallin 17021 Estonia
3 Lilly Smilkins Lilly Smilkin Matadsderos 2312 Eguero 14023 Mexico
4 Brandinina Tom Hitchins 110 Hanegover Sq. London WB2 2DP UK
5 Carizmos Christiano Kerrys Berguvsesvägen 9 Luleå S-968 43 Sweden

This is demo example from the "Orders" table in the database:

ID Customer_ID Employee_ID
20408 2 7
20409 2 5
85471 1 3
75864 5 8

SQL GROUP BY: Examples

In this example, we list the number of developers in each city:

Example
SELECT COUNT(ID), City
FROM Developers
GROUP BY City;

In this example, we list the number of developers in each city, sorted high to low:

Example
SELECT COUNT(ID), City
FROM Developers
GROUP BY City
ORDER BY COUNT(ID) DESC;

In this example, we list the number of orders done by each developer:

Example
SELECT Developers.Name, COUNT(Customer_orders.customer_id) AS OrdersCount 
FROM Customer_orders
LEFT JOIN Developers ON Customer_orders.customer_id = Developers.ID
GROUP BY Developers.Name;

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