HardSQL challenge #274WINDOW FUNCTIONRUNNING MAXANALYTICS

Calculate the Running Maximum Order Total

Return each order date with the largest order total seen up to that date.

The challenge runs on the SQLabHub practice database (SQLite) and uses the orders table. You can solve it in the browser, with nothing to install.

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The task

Find cumulative max order total over time.

A correct answer returns 200 rows with 2 columns: order_date, cum_max.

Tables used in this challenge

orders 200 rows

id INTEGER (PK) · user_id INTEGER · total REAL · discount REAL · item_count INTEGER · status TEXT · order_date TEXT · shipped_date TEXT · shipping_city TEXT · shipping_country TEXT

First 3 rows of the orders table
iduser_idtotaldiscountitem_countstatusorder_dateshipped_dateshipping_cityshipping_country
1432638.110.253cancelled2024-04-24NULLLos AngelesUSA
2829470.195delivered2024-03-152023-04-09ChicagoUSA
3136683.240.082delivered2023-02-152023-07-10Los AngelesUSA

The first rows of each table are shown. See how all the tables relate on the database schema page.

Expected output

Expected output of the challenge
order_datecum_max
2022-01-061843.49
2022-01-103920.44
2022-01-153920.44
2022-01-163920.44
2022-01-174163.77

First 5 of 200 rows. This is the output of the model solution on the practice database. The task does not fix a sort order, so your rows may come back in a different order.

What you practise

  • Accumulating a value row by row with an ordered window

Hint and approach

Try the challenge first. Open these only when you need them.

Show the hint

MAX OVER

Show the step-by-step approach

How the model solution is built, in the order the database evaluates it:

  1. Read from the orders table.
  2. Compute MAX(total) as a running window function: it covers the rows from the start up to the current one, ordered by order_date.

Model solution

Checking your session…

What to watch for

MAX() as a window function with ORDER BY keeps the record so far: the value changes only when a new high arrives. Swap in MIN() for a running minimum.

  • Running totals. With ORDER BY and no frame, rows that tie on the sort column are added together in one step. Use ROWS BETWEEN UNBOUNDED PRECEDING AND CURRENT ROW for a strict row-by-row total.
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Same technique, other tables

More practice on this pattern with different columns:

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