Test and Authenticate Your SQL Skills

SQL challenges can involve several technical and analytical capabilities rather than a single query type.

• SQL Fundamentals: SELECT, WHERE, ORDER BY, DISTINCT, LIMIT and basic expressions.
• Aggregation: COUNT, SUM, AVG, MIN, MAX, GROUP BY and HAVING.
• JOINs: INNER JOIN, LEFT JOIN, multiple-table joins and understanding table relationships.
• Subqueries and CTEs: Building intermediate results and structuring multi-step query logic.
• Window Functions: ROW_NUMBER, RANK, DENSE_RANK, LAG, LEAD, running totals and partitioned calculations.
• Conditional Logic: CASE expressions and rule-based categorisation.
• Date Functions: Date arithmetic, extraction, periods, cohorts and time-based comparisons.
• Data Cleaning With SQL: Handling NULLs, duplicates, inconsistent values and basic transformations.
• Query Debugging: Finding logic errors, unexpected duplicates, incorrect joins or faulty filters.
• Analytical Reasoning: Translating a business or data question into the correct query and interpreting the result.
  

SQL competitions can take different forms depending on the skill being tested.

• SQL Query ChallengesRetrieve specific information from one or more tables using filters, joins and aggregations.
• Data Analysis SQL ChallengesUse SQL to calculate metrics, identify trends, compare groups and answer business questions.
• JOIN ChallengesCombine related tables correctly and return the required records without duplication or missing data.
• CTE and Subquery ChallengesBreak complex logic into manageable steps or build intermediate query results.
• Window Function ChallengesCalculate rankings, running totals, moving values, partitions and comparisons across rows.
• Date and Time ChallengesWork with periods, intervals, cohorts, retention, monthly reporting and time-based calculations.
• Query Logic and Debugging ChallengesIdentify why a query produces an incorrect result and fix the logic.
• Real-World Analytics ProblemsUse SQL to answer questions related to customers, products, sales, marketing, finance or operations.

You do not need to be an SQL expert before getting started. The appropriate starting point depends on your current knowledge and what you want to demonstrate.

• Beginners Learning SQL

  Start with foundational challenges based on SELECT, filtering, sorting and simple aggregation, then progress gradually.

• Students

  Move beyond textbook queries and practise solving problems where the required SQL technique is not provided in advance.

• Aspiring Data Analysts

  Build experience with querying, joins, aggregation, business metrics and data interpretation.

• Data Analysts and BI Professionals

  Strengthen complex querying, reporting logic, window functions, CTEs and unfamiliar analytical scenarios.

• Data Scientists

  Improve data extraction, preparation and exploratory querying skills used before modelling and analysis.

• Data Engineers

  Practise transformations, query logic, table relationships and efficient retrieval.

• Career Switchers

  Use structured challenges to build practical evidence, then add authenticated proof of the capabilities you have developed.

   

• Hands-on SQL ExperienceUse SQL to reach an outcome instead of only memorising commands.

• Stronger Problem SolvingLearn how to translate questions into reliable query logic.

• Skill-Gap DiscoveryIdentify the SQL concepts and reasoning areas that need further practice.

• Skill BenchmarkingUse challenge scoring, evaluation or ranking where available to understand your practical level.

• Certificates and RecognitionEligible CompeteX challenges may provide certificates, rankings or rewards.

• Authenticated EvidenceAuthenX can provide an AI Performance Report, Authenticated Badge & Certificate, and Smart Ranking.

• Broader Proof of CapabilityCombine practical challenge performance with a separate authentication process to build a more complete picture of your skills.

• Sales Analysis

  A database contains customers, products and orders. Calculate monthly revenue, identify the strongest-performing product category and determine which customers made repeat purchases.

  Skills: JOINs, GROUP BY, date functions and aggregation.

• Customer RetentionUse transaction history to identify customers who returned within a defined period and calculate retention by acquisition month.
  
  Skills: CTEs, date logic, cohorts and conditional aggregation.

• RankingFind the top three products within each category based on revenue while preserving ties correctly.

  
  Skills: Aggregation, PARTITION BY, RANK or DENSE_RANK.

• Query DebuggingA query calculating total orders returns duplicated values after several tables are joined. Identify the cause and correct the query logic.

  Skills: JOIN logic, aggregation, debugging and validation.

• Review SQL fundamentals and common aggregate functions.

• Practise combining tables and validating JOIN logic.

• Use CTEs and subqueries to break complex questions into smaller steps.

• Become comfortable with window functions, ranking and time-based analysis.

• Work with real datasets and check row counts, duplicates, NULL values and output accuracy.

• Be prepared to explain why you chose a particular SQL approach, not only the final query.