Sign In | Feedback | Donate | Search
Katie and Emil Logo
Become a member*
No Ads Learner (Early Adopter)
for $1.99 per month Apply today!
* Members income helps develop more FREE content.

 

In this SQL tutorial I will cover SQL GROUP BY clause and give examples of how to use it. I will use SQL Server 2008 R2, but the examples in this tutorial should work with all SQL Server versions and some other databases. I will start with short and easy examples and explanations and move on to common group by questions that are slightly more involved.

Content:

 

SQL Group By Syntax

Below is group by syntax in the simpliest form:

SELECT FieldName

FROM TableName

GROUP BY FieldName

 

SQL Group By Example

Group By allows us to group rows together and additionally perform aggregate calculation which works on a group of rows. Let me first give you a simple example of what group by does using one field. I will use Customer table and group all customers by Country in other words I want to show all unique values that exist in Country Field, that is how group by works. See below example code with results (before and after)

SELECT *

from [dbo].[CUSTOMER]

 

SQL Group By clause

Group by example with Aggregate Function

You can group by fields in tables but this is rarely used on its own and very often that is combined with aggregate function. Aggregate function gets access to grouped rows. So if you group 3 rows into 1 then you can perform aggregate calculation like count which in this case would give result 3. You can also use other aggregate functions like SUM, MAX, MIN, AVG and several other ones. See below example that is the same as previous ones but now with Count aggregate function.

 

SELECT c.Country

,COUNT(*) as CustomerInEachCountry

,MAX(CustomerID) as TheHighestID

FROM dbo.Customer as c

GROUP BY c.Country


SQL Group by with aggregate function

Compare this example to previous one and you should understand how group by and aggregate function work using SQL. The count is performed on grouped rows so UK appear in results only once as it was grouped but there are 3 rows that contain country UK so when aggregate function is used it is applied to all rows "inside" the group therefore the result is 3. I also used MAX function with CustomerID field to get the highest customerID in each group.

Take care
Emil

 


Did you find this page helpful?
Vote Yes! Yes! [+0]  |  Vote no! No? [-0]

Author: by Katie Glownia
Upsss... Something went wrong and Google Ads on our website did not display.

Google ads sponsor FREE content on our website and without them it would not exist.

How to fix the problem?
  1. Check if the Google Search display any ads by searching the term Business Intelligence
    • If ads don't display, try different search terms and if there no ads then there might be a problem with your browser. If you made changes to your browser behaviour then undoing them will help.
    • If ads display then, refresh our page one more time, if the problem is still there than please contact us.
  2. Become 'No Ads Learner' Member or if you are already one Sign In.
Close
Take care
Katie & Emil
Well done! It seems Google Ads display properly now on our website.

Access our website's FREE content for FREE!