Help with Writing a Subquery to Get Aggregate Data in SQL Server

Question

Ravi Vishwakarma · Answer

To calculate the total sales for each customer using a subquery in SQL Server, you can use the GROUP BY clause along with an aggregate function like SUM.

Here’s an example query:

Assume you have a Sales table with columns CustomerID, SaleAmount, and SaleDate.

SELECT 
    CustomerID,
    (SELECT SUM(SaleAmount) 
     FROM Sales AS S 
     WHERE S.CustomerID = C.CustomerID) AS TotalSales
FROM 
    Customers AS C;

In this query:

The subquery (SELECT SUM(SaleAmount) FROM Sales AS S WHERE S.CustomerID = C.CustomerID) calculates the total sales for each customer.
The main query selects each CustomerID from the Customers table and uses the subquery to calculate the total sales for each customer.

Alternatively, you can achieve the same result without a subquery using a JOIN and GROUP BY:

select 
	C.CustomerID, 
	C.CustomerName, 
	SUM(SL.SaleAmount) AS Total 
from Customers AS C
INNER JOIN Sales AS SL ON C.CustomerID = SL.CustomerID
GROUP BY 
    C.CustomerID, C.CustomerName;

This approach joins the Customers and Sales tables and groups the results CustomerID to calculate the total sales.

Read more

How do I use the GROUP BY clause to aggregate data in SQL Server?

How to Join Multiple Tables and Retrieve Specific Columns in SQL Server?

Describe Common Table Expressions (CTEs) in SQL server.

How do I write CRUD operations to modify data in SQL Server tables?

forum

Help with Writing a Subquery to Get Aggregate Data in SQL Server

Can you answer this question?

1 Answers