Tables Used

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
transactiondate

The First Transaction Initiative :Find Each Customer’s Earliest Recorded Transaction Date Advanced

Q: Do I need advanced SQL to attempt this?

This problem is labeled as Advanced. It’s intended for learners who are already comfortable with common window functions and want to push into more complex analytical patterns. Don’t rush — work through the hints one at a time and study the final query structure carefully.

Find the very first recorded purchase for every galactic customer.

The galactic accounting department at Zlacksys 19 needs to identify the first transaction made by each customer. Write a query to display each customer's first transaction based on the transaction date.

Write Your Query

Answer:

          with rankedtransactions as
  (select customerid,
          transactionid,
          transactiondate,
          row_number() over (partition by customerid
                             order by transactiondate) as transactionrank
   from transaction)
select customerid,
       transactionid,
       transactiondate
from rankedtransactions
where transactionrank = 1;

This reflects tracking when customers first made a purchase to study onboarding, loyalty, or sales trends over time.

You’ll practice identifying first occurrences, organizing time-based data, and filtering for earliest records within groups.

This problem is labeled as Advanced. It’s intended for learners who are already comfortable with common window functions and want to push into more complex analytical patterns. Don’t rush — work through the hints one at a time and study the final query structure carefully.

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

The First Transaction Initiative :Find Each Customer’s Earliest Recorded Transaction Date Advanced

Find the very first recorded purchase for every galactic customer.

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)