Tables Used

orderdetails

Column	Type
orderdetailid	bigint
orderid	bigint
productid	bigint
quantity	bigint
unitprice	double precision
currencyid	bigint

orders

Column	Type
orderid	bigint
customerid	bigint
orderdate	timestamp without time zone
totalamount	double precision
status	text

products

Column	Type
productid	bigint
name	text
description	text
category	text
price	double precision
supplierid	bigint
stockquantity	bigint

Expected Output

Column
category
productname
nextproduct

Product Pairs in Category Time :Analyze Consecutive Product Sales and Category-Based Order Sequences Intermediate

Q: Do I need advanced SQL to attempt this?

This problem is labeled as Intermediate. It assumes you’ve written a few window function queries before, but you don’t need to be an expert. Use the hints and explanations if you get stuck — they’re there to help you think through the logic.

List each product sale and the next item sold in its category by date.

Xorthax is studying sales trends by category. Write a query to display each product sold and the next product sold within the same category, based on the order date.

Write Your Query

Answer:

          select p.category,
       p.name as productname,
       lead(p.name) over (partition by p.category
                          order by o.orderdate asc) as nextproduct
from orderdetails od
join orders o on od.orderid = o.orderid
join products p on od.productid = p.productid;

This models sales pattern analysis, where businesses track consecutive product sales within categories to understand buying trends.

You’ll practice comparing sequential records within grouped data to analyze event order and relational patterns.

This problem is labeled as Intermediate. It assumes you’ve written a few window function queries before, but you don’t need to be an expert. Use the hints and explanations if you get stuck — they’re there to help you think through the logic.

Yes. Every problem comes with optional hints you can reveal one at a time, plus a fully worked step-by-step solution. You decide how much help you want while practicing.

All problems on PracticeWindowFunctions.com are completely free and can be solved without creating an account. Right now there are over 80 practice problems, with new ones added regularly.

SQL Cookbook (O’Reilly)

Practical SQL recipes for real-world querying—great complement to hands-on practice.

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Tables Used

Expected Output

Product Pairs in Category Time :Analyze Consecutive Product Sales and Category-Based Order Sequences Intermediate

List each product sale and the next item sold in its category by date.

What real-world scenario does this represent?

What SQL concepts will I practice here?

Do I need advanced SQL to attempt this?

Will I get hints and step-by-step explanations if I get stuck?

Are the problems free to access, and how many are available?

SQL Cookbook (O’Reilly)