Skolarli SQL tutorials are hands-on, step-by-step walkthroughs you can follow and run. Each one answers a single concrete question, shows the working code, and explains the tradeoffs.
General
Fifteen SQL interview questions for intermediate to senior data, backend, and analytics candidates, covering joins, aggregation, subqueries, and window functions, with working queries and the efficiency trade-offs interviewers listen for. Assumes familiarity with basic SELECT, WHERE, and GROUP BY.
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Ten practical query-writing questions covering pagination, CASE logic, date ranges, CTEs, and upserts, the everyday patterns that come up as often as joins but rarely get grouped together. Each question pairs a working query with a less scalable alternative and the trade-off between them.
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Ten questions on join types and the mistakes that break them in production, including the single most common bug: filtering a LEFT JOIN's matched table in WHERE instead of ON. Built for candidates who already know basic SELECT and want to go deeper specifically on joins.
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A framework for assessing SQL-heavy candidates across four dimensions, query correctness, performance at scale, schema design judgment, and data integrity habits, calibrated by seniority. Built for hiring managers screening data analysts, data engineers, and backend roles with significant SQL responsibility.
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Ten advanced questions on when a correlated subquery quietly re-runs per row versus when a window function computes the same result in one pass, plus the window-frame default that trips up even experienced candidates. Built for candidates who already know basic joins and ranking functions like RANK and ROW_NUMBER.
Read tutorialEvery tutorial opens with a direct answer to the question in its title, then walks through the working solution step by step. Code you can copy sits in a syntax-highlighted block. Tutorials that belong to a series are ordered from beginner to advanced so you can follow a path rather than hunt for the next piece.
Looking to sharpen judgment rather than complete a task — interviews, career moves, what to look for when applying? Those live in Guides.
For hiring & L&D teams
These tutorials are also where teams come to shape their question banks. If you're putting together coding assessments, technical screens, or a question library for hiring or training, Skolarli's assessment platform does it at scale — with proctoring and integrity built in. Tell us what you're assessing for.