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

suppliers

Column	Type
supplierid	bigint
name	text
originplanet	text
contactinfo	text
rating	double precision

Expected Output

Column
suppliername
lastorderdate

Last Fulfillments by Supplier :Find Each Supplier’s Most Recent Fulfilled Order and Delivery Date 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.

Reveal the final order date handled by each interstellar supplier.

The suppliers guild wants to find the last order fulfilled by each supplier. Write a query to display the last order date for each supplier.

Write Your Query

Answer:

          select distinct s.name as suppliername,
                LAST_VALUE(o.orderdate) over (partition by s.supplierid
                                              order by o.orderdate,
                                                       o.orderid rows between unbounded PRECEDING and unbounded following) as lastorderdate
from orderdetails od
join orders o on od.orderid = o.orderid
join products p on od.productid = p.productid
join suppliers s on p.supplierid = s.supplierid
order by suppliername;

This mirrors supplier performance tracking, where companies review the most recent fulfillment dates to monitor activity and responsiveness.

You’ll practice grouping supplier data, ordering by fulfillment dates, and isolating the most recent event within each supplier’s record set.

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

Last Fulfillments by Supplier :Find Each Supplier’s Most Recent Fulfilled Order and Delivery Date Intermediate

Reveal the final order date handled by each interstellar supplier.

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)