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Top Dynamic Categories Per User
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Top Dynamic Categories Per User

HardSQL · PostgreSQL

Problem

Write a query to find the top three spending categories for each user over the last 90 days, ranking them dynamically at Truebill.

Assume the reporting date is 2025-04-01. Include positive, non-null transactions from the 90-day period ending immediately before that date.

Output

  1. One row per user and qualifying category, limited to the top three categories for each user.
  2. Columns: user_id, user_name, category_name, total_spent, and category_rank.
  3. Rank by total spending descending, with category name ascending as the tie-breaker.
  4. Order by user_id, then category_rank.

Schema

users
ColumnTypeDescription
user_idPKINTUnique Truebill user identifier
user_nameVARCHAR(100)User display name
spending_categories
ColumnTypeDescription
category_idPKINTUnique spending category identifier
category_nameVARCHAR(100)Spending category name
transactions
ColumnTypeDescription
transaction_idPKINTUnique transaction identifier
user_idINTUser who made the transaction
category_idINTAssociated spending category
transaction_dateDATEDate the transaction occurred
amountNUMERIC(12,2)Transaction amount in dollars
Tablesuserstransactionsspending_categories
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