--- title: SQL Interview Problem: The Suspicious Split (+ 2... description: A walkthrough of a SQL interview problem called 'The Suspicious Split,' where employees may be splitting large expenses into two smaller transactions to avoid... canonical: https://daily.dev/posts/sql-interview-problem-the-suspicious-split-2-challenges-to-solve-yourself--5yazwipqg twitter:card: summary_large_image twitter:site: @dailydotdev og:type: website og:site_name: daily.dev og:title: SQL Interview Problem: The Suspicious Split (+ 2 Challenges to Solve Yourself) | daily.dev og:description: A walkthrough of a SQL interview problem called 'The Suspicious Split,' where employees may be splitting large expenses into two smaller transactions to avoid... og:url: https://daily.dev/posts/sql-interview-problem-the-suspicious-split-2-challenges-to-solve-yourself--5yazwipqg og:image: https://api.daily.dev/og/posts/5YAzWIPqG.png og:image:alt: SQL Interview Problem: The Suspicious Split (+ 2 Challenges to Solve Yourself) og:image:width: 1200 og:image:height: 630 og:locale: en --- > ## Documentation Index > Fetch the complete documentation index at: https://daily.dev/llms.txt > Use this file to discover all available pages before exploring further. # SQL Interview Problem: The Suspicious Split (+ 2 Challenges to Solve Yourself) **[techTFQ](https://daily.dev/sources/techtfq)** · 18 min read · 0 upvotes · 0 comments ## Summary A walkthrough of a SQL interview problem called 'The Suspicious Split,' where employees may be splitting large expenses into two smaller transactions to avoid manager approval thresholds. The solution uses a self join on an expense transactions table, joining on employee ID with a transaction ID inequality to avoid duplicate pairs, then filtering on individual amounts under $1,000, combined amount over $1,000, and a date difference of 3 days or less using ABS(). Two additional premium problems (Peak Hour and Bundle Completionist) are left as challenges, both free for one week on SQL Nest before requiring a premium subscription. ## Full article daily.dev links to this article rather than hosting it. Read it at the original source: ## Questions this post answers ### How do you write a SQL query to detect employees splitting a large expense into two smaller transactions to avoid approval thresholds? Use a self join on the transactions table, joining on employee id with a condition like t1.transaction_id < t2.transaction_id to avoid duplicate pairs. Add filters so both amounts are under 1000, their sum is 1000 or more, and abs(t1.date - t2.date) is less than or equal to 3 days, then order by combined amount descending. _daily.dev surfaces SQL self-join techniques like this for developers building fraud or anomaly detection queries._ ### Why use a self join instead of LEAD or LAG window functions to compare transactions within the same group in SQL? A self join lets every transaction row be compared against every other transaction row for the same employee, which is necessary here because a qualifying pair does not have to be adjacent in the data or the next chronological transaction. LEAD and LAG only compare a row to its immediate neighbor in an ordered sequence, so they would miss non-adjacent matching pairs. _developers weighing self joins versus window functions can find comparisons like this through daily.dev._ ## Similar posts on daily.dev - [10 Simple Steps to Solve SQL Problems \[2026\]](https://daily.dev/posts/10-simple-steps-to-solve-sql-problems-2026--uicxpyy02) · Planet MySQL · 0 upvotes · 0 comments - [Six SQL patterns I use to catch transaction fraud](https://daily.dev/posts/six-sql-patterns-i-use-to-catch-transaction-fraud-0vozg6gea) · Hacker News · 0 upvotes · 0 comments - [Project 1: Customer Intelligence Layer — Findings](https://daily.dev/posts/project-1-customer-intelligence-layer-findings-vtppzsyxj) · Medium · 0 upvotes · 0 comments - [NOLOCK Double Counting: One Employee, Two Lunches](https://daily.dev/posts/nolock-double-counting-one-employee-two-lunches-luwupnpiz) · SQL Authority · 0 upvotes · 0 comments --- Tags: [#sql](https://daily.dev/tags/sql), [#interview-questions](https://daily.dev/tags/interview-questions) [View this post on daily.dev](https://daily.dev/posts/sql-interview-problem-the-suspicious-split-2-challenges-to-solve-yourself--5yazwipqg) ```json {"@context":"https://schema.org","@graph":[{"@type":"Organization","@id":"https://daily.dev/#organization","name":"daily.dev","url":"https://daily.dev","logo":{"@type":"ImageObject","url":"https://daily.dev/apple-touch-icon.png","width":180,"height":180},"sameAs":["https://twitter.com/dailydotdev","https://github.com/dailydotdev","https://www.linkedin.com/company/daily-dev-ltd"]},{"@type":"WebSite","@id":"https://daily.dev/#website","url":"https://daily.dev","name":"daily.dev","publisher":{"@id":"https://daily.dev/#organization"},"potentialAction":{"@type":"SearchAction","target":{"@type":"EntryPoint","urlTemplate":"https://daily.dev/search?q={search_term_string}"},"query-input":"required name=search_term_string"}}]} 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