2026

SQL Interview Questions 2026

A current, 2026 snapshot of the SQL interview questions worth knowing — kept up to date as frameworks and best practices evolve, so you prepare with what companies are actually asking in 2026.

119Questions14Beginner12Intermediate93Senior

119 SQL questions

  1. 1What is an execution plan?Intermediate
  2. 2What are isolation levels?Intermediate
  3. 3What are ACID properties?Intermediate
  4. 4What is denormalization?Intermediate
  5. 5What is normalization?Intermediate
  6. 6What is an index in SQL?Intermediate
  7. 7What are window functions?Intermediate
  8. 8What is a CTE?Intermediate
  9. 9What is a subquery?Intermediate
  10. 10What is ORDER BY and LIMIT?Beginner
  11. 11What is a foreign key?Beginner
  12. 12What is a primary key?Beginner
  13. 13What is HAVING clause?Beginner
  14. 14What is GROUP BY?Beginner
  15. 15What is a LEFT JOIN?Beginner
  16. 16What is INNER JOIN?Beginner
  17. 17What is a WHERE clause?Beginner
  18. 18What is a SELECT statement?Beginner
  19. 19What is SQL and why is it used?Beginner
  20. 20SQL Interview Question 2 (Free)Intermediate
  21. 21SQL Interview Question 1 (Free)Beginner
  22. 22SQL Interview Question 5 (Free)Intermediate
  23. 23SQL Interview Question 4 (Free)Beginner
  24. 24SQL Interview Question 3 (Free)Senior
  25. 25What is secondary index inconsistency in distributed databases?Senior
  26. 26What is data locality in distributed SQL systems?Senior
  27. 27What is query timeout strategy?Senior
  28. 28What is database backpressure?Senior
  29. 29What is write quorum consistency vs read quorum consistency?Senior
  30. 30What is database sharding rebalancing?Senior
  31. 31What is global vs local indexing in partitioned tables?Senior
  32. 32What is table partitioning strategy?Senior
  33. 33What is index intersection strategy?Senior
  34. 34What is hybrid transactional/analytical processing (HTAP)?Senior
  35. 35What is adaptive query optimization?Senior
  36. 36What is materialized aggregation vs runtime aggregation?Senior
  37. 37What is event sourcing in databases?Senior
  38. 38What is CQRS pattern in database systems?Senior
  39. 39What is query fan-out problem?Senior
  40. 40What is sharding key selection strategy?Senior
  41. 41What is partition pruning?Senior
  42. 42What is bloom filter in SQL and storage systems?Senior
  43. 43What is read amplification?Senior
  44. 44What is write amplification in databases?Senior
  45. 45What is index-only scan?Senior
  46. 46What is a materialized view refresh strategy?Senior
  47. 47What is anti-join pattern in SQL optimization?Senior
  48. 48What is hinted handoff in distributed databases?Senior
  49. 49What is read repair in distributed databases?Senior
  50. 50What is data skew in SQL and distributed systems?Senior
  51. 51What is zero downtime migration?Senior
  52. 52What is schema evolution in databases?Senior
  53. 53What is eventual convergence in distributed systems?Senior
  54. 54What is quorum in distributed databases?Senior
  55. 55What is multi-master replication?Senior
  56. 56What is snapshot isolation in databases?Senior
  57. 57What is write skew anomaly?Senior
  58. 58What is isolation anomaly in SQL transactions?Senior
  59. 59What is lock escalation in databases?Senior
  60. 60What is database deadlock detection and resolution strategy?Senior
  61. 61What is database buffer pool?Senior
  62. 62What is database log compaction?Senior
  63. 63What is dead tuple in MVCC systems?Senior
  64. 64What is database vacuuming?Senior
  65. 65What is a merge join?Senior
  66. 66What is a nested loop join?Senior
  67. 67What is a hash join in SQL execution?Senior
  68. 68What is query hinting in SQL?Senior
  69. 69What is a histogram in database statistics?Senior
  70. 70What is query cardinality estimation?Senior
  71. 71What is a full table scan and why is it expensive?Senior
  72. 72What is a clustered index vs non-clustered index?Senior
  73. 73What is a database checkpoint?Senior
  74. 74What is index fragmentation and how does it impact performance?Senior
  75. 75What is query throttling in databases?Senior
  76. 76What is database indexing trade-off?Senior
  77. 77What is a write-ahead log (WAL)?Senior
  78. 78What is query parallelism in databases?Senior
  79. 79What is database connection pooling?Senior
  80. 80What is advanced indexing (GIN, GiST, BRIN)?Senior
  81. 81What is query result caching vs materialized views?Senior
  82. 82What is read/write splitting in databases?Senior
  83. 83What is horizontal vs vertical scaling in databases?Senior
  84. 84What is query execution bottleneck analysis?Senior
  85. 85What is indexing strategy in large-scale systems?Senior
  86. 86What is CAP theorem?Senior
  87. 87What is eventual consistency vs strong consistency?Senior
  88. 88What is two-phase commit (2PC)?Senior
  89. 89What is ACID compliance in distributed databases?Senior
  90. 90What is query planner in SQL databases?Senior
  91. 91What is eventual consistency?Senior
  92. 92What is read replica lag?Senior
  93. 93What is consistent hashing in databases?Senior
  94. 94What is a hot shard problem?Senior
  95. 95What is database normalization vs denormalization trade-off?Senior
  96. 96What is a bitmap vs B-tree index?Senior
  97. 97What is predicate pushdown?Senior
  98. 98What is query caching?Senior
  99. 99What is a bitmap index?Senior
  100. 100What is indexing selectivity?Senior
  101. 101What is a CROSS JOIN?Senior
  102. 102What is a self join?Senior
  103. 103What is a correlated subquery?Senior
  104. 104What is query execution order in SQL?Senior
  105. 105What is OLTP vs OLAP?Senior
  106. 106What are materialized views?Senior
  107. 107What is MVCC?Senior
  108. 108What is locking in databases?Senior
  109. 109What are deadlocks in SQL?Senior
  110. 110How do you optimize SQL queries?Senior
  111. 111What is replication in SQL databases?Senior
  112. 112What is sharding in databases?Senior
  113. 113What is database partitioning?Senior
  114. 114What are indexes and how do they improve performance?Senior
  115. 115SQL Advanced Interview Question 8Intermediate
  116. 116SQL Advanced Interview Question 9Senior
  117. 117SQL Advanced Interview Question 10Beginner
  118. 118SQL Advanced Interview Question 6Senior
  119. 119SQL Advanced Interview Question 7Beginner

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Are these SQL interview questions up to date for 2026?

Yes. This page reflects 119 SQL interview questions kept current with today's frameworks, tooling and interview trends, with each answer maintained and dated.

What SQL topics should I focus on in 2026?

Prioritise the fundamentals plus the modern patterns interviewers ask about now. Each question here includes a detailed answer, code example and common mistakes so you can target the highest-impact areas.

Are these questions free?

You can read the question and a short answer for free. A subscription unlocks the full detailed explanation, real-world example, common mistakes and follow-up questions for each one.