SQL Server Coding Challenges: Query Challenges Tutorial

Find Customers with No Orders

Write a query to list customers who have never placed an order.

Expected output: List of customers without matching orders.

Hint: Use LEFT JOIN and check for NULL in the orders table.

Calculate Running Total of Sales

Write a query to calculate the running total of sales ordered by date.

Expected output: Sales data with an additional column showing running totals.

Hint: Use the SUM() window function with ORDER BY.

Rank Products by Sales in Each Category

Write a query to rank products by total sales within their category.

Expected output: Products ranked by sales per category.

Hint: Use ROW_NUMBER() partitioned by category.

INNER JOIN returns rows with matching values in both tables, while LEFT JOIN returns all rows from the left table and matching rows from the right table, or NULL if no match exists.

Window functions perform calculations across a set of rows related to the current row without collapsing the result set, whereas aggregate functions summarize multiple rows into a single result.

A correlated subquery is a subquery that references columns from the outer query, executing once per row of the outer query.