SQLMaxx
Sign in Start free
N045-E3 Tier 4 · Advanced · easy ecommerce · Brightlane

Return every order's ID, status, total amount, and the order's spend tier within its status group. Sort the final result by `status` ascending, then `total_amount` ascending

Part of NTILE and Percentile Functions in SQL

The problem

Brightlane's operations team wants every order divided into three spend tiers within its order-status group for internal benchmarking.

Write a query to return every order's ID, status, total amount, and the order's spend tier within its status group. Sort the final result by status ascending, then total_amount ascending.

Assumptions:

  • Within each status, orders are sorted by total_amount ascending and assigned to one of three tiers based on position. Tier 1 covers the lowest-value third of orders in that status; tier 3 covers the highest-value third.
  • Tier numbering restarts within each status.
  • When the row count within a status does not divide evenly by 3, the earlier tiers each receive one extra record.
  • The final result is sorted by status ascending, then by total_amount ascending.

Output:

  • One row per order, with columns id, status, total_amount, and spend_tier. Sorted by status, then total_amount.
Schema · ecommerce 5 tables
categories
id integer
name text
parent_id? integer
products
id integer
name text
category_id integer
price numeric
stock_qty integer
attributes? jsonb
order_items
id integer
order_id integer
product_id integer
quantity integer
unit_price numeric
customers
id integer
name text
email text
city? text
country text
created_at timestamptz
is_active boolean
orders
id integer
customer_id integer
ordered_at timestamptz
status text
total_amount numeric
Check answerShift Ctrl ↵

Run previews · Check grades

Write a query, then run it to see results here.
Worked solution Try it yourself first
Solution query
SELECT
  id,
  status,
  total_amount,
  NTILE(3) OVER (
    PARTITION BY
      status
    ORDER BY
      total_amount
  ) AS spend_tier
FROM
  orders
ORDER BY
  status,
  total_amount

The shape

PARTITION BY status resets the bucketing inside each status group, so NTILE(3) cuts each status's orders into three equal-row spend tiers independently. Every order keeps its status, its dollar amount, and picks up a tier that ranges from 1 to 3 within its own status. The outer sort prints each status's orders together, ascending by amount.

Clause by clause

  • SELECT id, status, total_amount, NTILE(3) OVER (PARTITION BY status ORDER BY total_amount) AS spend_tier returns the order's identifying columns and its within-status tier. PARTITION BY status is what makes the tier numbering restart at 1 for each status; ORDER BY total_amount defines the ascending sort the buckets are cut from inside each partition.
  • FROM orders reads every order across every status. No WHERE filter.
  • ORDER BY status, total_amount is the outer sort. It prints all of one status's orders together, in ascending value, before moving to the next status.

Why this and not running NTILE without PARTITION BY

Without PARTITION BY status, NTILE(3) would cut the entire order set into three buckets and a delivered order with a small dollar amount could share tier 1 with a pending order of the same dollar amount. The operations team's benchmark is within-status: each status is its own population, and tier 1 means "the bottom third of orders in this particular status." The partition is what enforces that frame.

The trap

Tier numbers reset across statuses, so a tier-3 row in pending is not directly comparable to a tier-3 row in delivered. Each status has its own scale. Anyone reading the result has to read the tier in context with the status column; the tier number on its own is meaningless.

You practiced NTILE(3) OVER (PARTITION BY ... ORDER BY ...) — per-partition bucket distribution; tier numbering restarts in each group.

How you actually get good at SQL

Reading explains SQL. Writing it, over and over with instant feedback, is what makes you fluent.

That's the whole SQLMaxx loop: 600+ real problems, instant AI feedback, mastery you can actually see, and spaced review that won't let you forget.

A stack of SQL practice problem cards, the top card showing an employees table.
615 problems · 66 concepts

Real problems. Not toy examples.

615 hand-built problems spanning all 66 concepts, from basic SELECTs to window functions, built on real schemas and real business questions, the kind you'll actually get asked on the job. Enough reps to make SQL automatic.

A retro computer showing a SQL query marked correct with a green checkmark.
Instant AI feedback

Write a query. Know if it's right in one second.

No copying an answer and hoping it clicked. The AI grader checks your real query against real data, catches exactly what's wrong, and explains the fix in plain English, like a senior analyst reading over your shoulder on every problem.

A circular mastery progress dial filling from blue to green, the SQLMaxx diamond at its center.
Mastery tracking

Stop guessing whether you actually know it.

SQLMaxx tracks every concept and shows you what you've mastered and what's still shaky. Your skills fill in one concept at a time, so 'I think I get joins' becomes something you can prove.

A SQL query editor circled by a blue return arrow with a clock, scheduled to come back for review.
Spaced review

Learn it once. Keep it for good.

Most of what you learn this week fades by next week. So when a concept comes due for review, SQLMaxx hands you a fresh problem to solve from a blank editor, not a flashcard to re-read. A research-backed spaced-repetition algorithm (FSRS) times each return for right before you'd forget, so your SQL is still there months later, when the interview or the job actually needs it.

Practice, feedback, mastery, review. That's the loop that turns reading into real skill.

Start free

No account, no credit card. Start solving in under a minute.