Tables Used

orders

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

transaction

Column	Type
transactionid	bigint
orderid	bigint
customerid	bigint
supplierid	bigint
transactiontype	text
amount	double precision
currencyid	bigint
transactiondate	text
paymentmethod	text
description	text
status	text
createdat	text
updatedat	text

Expected Output

Column
customerid
transactionid
totalamount
secondnexttransactionid
secondnexttransactionamount

Future Funds Forecast :Track Each Customer’s Current and Second Upcoming Transaction Details 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.

For every transaction, show the second upcoming purchase for that customer if available.

The accounting team at Xorthax's trading post is forecasting customer activity. Write a query to show each transaction along with the ID and amount of the customer's second upcoming transaction, if one exists.

Write Your Query

Answer:

          with transaction_details as
  (select o.customerid,
          t.transactionid,
          o.totalamount,
          lead(t.transactionid, 2) over (partition by o.customerid
                                         order by t.transactiondate asc) as secondnexttransactionid,
                                        lead(o.totalamount, 2) over (partition by o.customerid
                                                                     order by t.transactiondate asc) as secondnexttransactionamount
   from orders o
   join transaction t on o.orderid = t.orderid)
select customerid,
       transactionid,
       totalamount,
       secondnexttransactionid,
       secondnexttransactionamount
from transaction_details;

This represents customer forecasting where analysts review past and future transactions to predict upcoming purchasing activity.

You’ll practice comparing sequential transactions within customer histories to analyze forward-looking financial relationships.

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 for Data Analysis (O’Reilly)

SQL techniques tailored for analytics and reporting workflows.

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Tables Used

Expected Output

Future Funds Forecast :Track Each Customer’s Current and Second Upcoming Transaction Details Intermediate

For every transaction, show the second upcoming purchase for that customer if available.

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 for Data Analysis (O’Reilly)