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Interview Questions Guides & Tutorials
Curated interview question banks with answers — SQL, Python, data science, Spark, Power BI, AWS, ADF and more.
Interview Questions articles
Window Functions SQL Interview Questions
Interviewers use window functions to see whether you understand how SQL evaluates a query, not just the syntax. These nine questions, each answered with a query run on two years of real bike rentals, cover ranking ties, top N per group, running totals, the default frame trap, gaps and islands, and filtering.
Data Warehouse Interview Questions and Answers
Data warehouse interviews ask how the platform behaves, not just what terms mean. Six questions answered on millions of real New York taxi trips: why columnar files are smaller, how partition pruning skips data, why reloads duplicate rows, what schema drift looks like, where stray rows go, and when to summarise.
Feature Engineering Interview Questions
Feature engineering questions test judgement about what a model may know and how it sees the data. Six questions are answered with measurements on 41,188 real bank calls: a leaky feature worth 0.15 AUC, when scaling matters, target encoding done wrong, informative unknowns, U-shaped effects and misleading importances.
Machine Learning Interview Questions: Concepts and Answers
Machine learning concept questions are easy to answer with definitions and hard to answer well. Seven core concepts are shown here in numbers from 30,000 real credit card clients: the accuracy trap, overfitting by tree depth, L1 regularisation, thresholds, calibration, cross-validation spread and learning curves.
SQL Joins Interview Questions Explained
Join questions in interviews are rarely about syntax. They test whether you can predict how many rows come back. These nine questions, each answered with a query on three million real New York taxi trips, cover anti-joins, ON versus WHERE, NOT IN with NULLs, fan-out, self-joins, calendars and full outer joins.
Tableau Interview Questions and Answers
Tableau interviews return to one topic more than any other: when each calculation happens. This guide answers the core questions on FIXED, INCLUDE and table calculations, with the Tableau formulas and their results reproduced on a year of real online orders: one filter, two answers, 100% or 2.57%.