12 Histogram Of Users And Purchases

Walmart

Interview Core Track · Hard · 35 min

-- Assume you're given a table on Walmart user transactions. Based on their most recent transaction date, write a query that retrieve the users along with th...

Interview Core Track

Hard

35 min

aggregation

Company labels are directional practice context, not official interview guidance.

Timer 00:00

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Objective

Practice aggregation through a Walmart-tagged business scenario.

Approach

Use this track to improve speed, edge-case handling, and accuracy under timed conditions.

Company context

Company labels are directional practice context, not official interview guidance.

Prereq: query basics

Prereq: filtering

-- Assume you're given a table on Walmart user transactions. Based on their most recent transaction date, write a query that retrieve the users along with the number of products they bought. -- Output the user's most recent transaction date, user ID, and the number of products, sorted in chronological order by the transaction date. -- Solution : completed on first attempt with most_recent_transaction as ( SELECT *, RANK() OVER(PARTITION BY user_id ORDER BY transaction_date desc) as rank FROM user_transactions ) SELECT transaction_date, user_id, COUNT(product_id) as purchase_count FROM most_recent_transaction WHERE rank=1 GROUP BY 1, 2 ORDER BY 1

user_transactions

transaction_id INT PRIMARY KEY

user_id INT NOT NULL

transaction_date DATE NOT NULL

product_id INT NOT NULL

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