Understand Group by Clause in SQL Server - SQL Server / TSQL Tutorial Part 130

Scenario: 

You are working as SQL Server Developer. You have a dbo.Customer table which has CountryShortName and SaleAmount. You are asked to write a query that should return Sum of SaleAmount , count of records by CountryShortName.

Solution:

Group by clause is often used with aggregate functions such as Sum, Avg,Count,Max,Min to group the result set by column/s.

Let's create our sample table with some data and write our query with Group by to answer our question.

Create table dbo.Customer
 (Id int,
  FName VARCHAR(50),
  LName VARCHAR(50),
  CountryShortName CHAR(2),
  SaleAmount Int)
GO
--Insert Rows in dbo.Customer Table
insert into dbo.Customer
Values (
1,'Raza','M','PK',10),
(2,'Rita','John','US',12),
(3,'Sukhi','Singh',Null,25),
(4,'James','Smith','CA',60),
(5,'Robert','Ladson','US',54),
(6,'Alice','John','US',87),
(6,'John',Null,'US',Null)

Let's write our query by using Sum, Count and Group by Clause

SELECT Sum(saleamount) AS TotalSaleByCountry, 
       Count(*) AS RecordCountByCountry, 
       countryshortname 
FROM   dbo.customer 
GROUP  BY countryshortname

How to use Group by Clause in SQL Server

You can also use multiple columns in group by clause. think about if our table would have states and you would like to group by CountryShortName and State, You would simple include State in query as shown below.

SELECT Sum(saleamount) AS TotalSaleByCountry, 
       Count(*) AS RecordCountByCountry, 
       countryshortname,

       [State]
FROM   dbo.customer 
GROUP  BY countryshortname,[State]

Video Demo: What is Group by Clause in SQL Server