2026

T-SQL Interview Questions 2026

A current, 2026 snapshot of the T-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.

143Questions14Beginner13Intermediate116Senior

143 T-SQL questions

  1. 1What is CASE expression?Intermediate
  2. 2What is a SQL function?Intermediate
  3. 3What is a stored procedure?Intermediate
  4. 4What is a VIEW in SQL Server?Intermediate
  5. 5What are transactions in SQL Server?Intermediate
  6. 6What is an index in SQL Server?Intermediate
  7. 7What is DISTINCT?Intermediate
  8. 8What is HAVING clause?Intermediate
  9. 9What is GROUP BY?Intermediate
  10. 10Difference between INNER and LEFT JOINIntermediate
  11. 11What is JOIN in T-SQL?Beginner
  12. 12What is NULL in SQL Server?Beginner
  13. 13What is FOREIGN KEY?Beginner
  14. 14What is PRIMARY KEY?Beginner
  15. 15What is DELETE statement?Beginner
  16. 16What is UPDATE statement?Beginner
  17. 17What is INSERT statement?Beginner
  18. 18What is ORDER BY clause?Beginner
  19. 19What is WHERE clause in T-SQL?Beginner
  20. 20What is SELECT statement in T-SQL?Beginner
  21. 21T-SQL Interview Question 2 (Free)Intermediate
  22. 22T-SQL Interview Question 5 (Free)Intermediate
  23. 23T-SQL Interview Question 4 (Free)Beginner
  24. 24T-SQL Interview Question 3 (Free)Senior
  25. 25T-SQL Interview Question 1 (Free)Beginner
  26. 26What is SQL Server execution plan XML structure and operator tree representation?Senior
  27. 27What is SQL Server internal memory pressure detection and eviction policy?Senior
  28. 28What is SQL Server statistics incremental update mechanism for partitioned tables?Senior
  29. 29What is SQL Server internal deadlock detection graph cycle resolution algorithm?Senior
  30. 30What is SQL Server internal parallel query partitioning strategy (hash, range, round robin)?Senior
  31. 31What is SQL Server memory grant feedback loop instability problem?Senior
  32. 32What is SQL Server automatic tuning and force last good plan mechanism?Senior
  33. 33What is SQL Server hybrid buffer pool and persistent memory optimization?Senior
  34. 34What is SQL Server columnstore batch mode execution pipeline and how does vectorization work internally?Senior
  35. 35What is SQL Server transaction isolation level escalation effects on concurrency?Senior
  36. 36What is SQL Server internal index seek vs scan decision boundary?Senior
  37. 37What is SQL Server deadlock priority and victim selection algorithm?Senior
  38. 38What is SQL Server internal logging buffer and log flush mechanism?Senior
  39. 39What is SQL Server filtered execution plan behavior under parameterization?Senior
  40. 40What is SQL Server indirect memory pressure and stolen memory behavior?Senior
  41. 41What is SQL Server compilation pipeline cost breakdown model?Senior
  42. 42What is SQL Server adaptive query processing (AQP) family and how does it evolve plans?Senior
  43. 43What is SQL Server internal query execution context (task, worker, request) relationship?Senior
  44. 44What is SQL Server identity allocation and identity cache behavior?Senior
  45. 45What is SQL Server filtered index and how does optimizer leverage it?Senior
  46. 46What is SQL Server deferred name resolution and its use cases?Senior
  47. 47What is SQL Server memory grant spill and how does it impact query execution?Senior
  48. 48What is SQL Server tempdb allocation contention (PFS, GAM, SGAM bottlenecks)?Senior
  49. 49What is SQL Server CXPACKET vs CXCONSUMER wait internal difference?Senior
  50. 50What is SQL Server columnstore segment elimination at storage engine level?Senior
  51. 51What is SQL Server internal query execution thread scheduling (SOS Scheduler) and how does it manage CPU?Senior
  52. 52What is SQL Server resource semaphore and memory grant starvation?Senior
  53. 53What is SQL Server indirect checkpoint and its performance implications?Senior
  54. 54What is SQL Server compiled plan vs execution plan difference?Senior
  55. 55What is SQL Server parallel execution exchange operators (distribute, repartition, gather)?Senior
  56. 56What is SQL Server tempdb version store and row versioning mechanism?Senior
  57. 57What is SQL Server statistics histogram density vector deep structure?Senior
  58. 58What is SQL Server plan cache pollution and how does it degrade performance?Senior
  59. 59What is SQL Server latch-free architecture in In-Memory OLTP internals?Senior
  60. 60What is SQL Server internal memory architecture (clerks, nodes, grants, and pressure signals)?Senior
  61. 61What is SQL Server execution plan recompilation and its causes?Senior
  62. 62What is SQL Server execution context switching overhead?Senior
  63. 63What is SQL Server columnstore index compression architecture?Senior
  64. 64What is SQL Server tempdb architecture and modern best practices?Senior
  65. 65What is SQL Server wait statistics and how do you interpret them?Senior
  66. 66What is SQL Server statistics auto-update threshold and its limitations?Senior
  67. 67What is SQL Server deadlock graph and how do you analyze it?Senior
  68. 68What is SQL Server buffer pool extension and how does it improve memory management?Senior
  69. 69What is SQL Server query execution pipeline from query parsing to result delivery?Senior
  70. 70What is SQL Server extended events and how is it better than Profiler?Senior
  71. 71What is statistics auto-update and auto-create behavior in SQL Server?Senior
  72. 72What is SQL Server snapshot isolation and how does it prevent blocking?Senior
  73. 73What is In-Memory OLTP (Hekaton) in SQL Server?Senior
  74. 74What is SQL Server partitioning and how does partition elimination work?Senior
  75. 75What is SQL Server Always On Availability Groups internal architecture?Senior
  76. 76What is HADR (High Availability Disaster Recovery) in SQL Server?Senior
  77. 77What is SQL Server lock escalation and how does it work internally?Senior
  78. 78What is parameter sniffing in SQL Server and how do you fix it?Senior
  79. 79What is SQL Server Query Optimizer architecture and how does it generate execution plans?Senior
  80. 80What is SQL Server resource governor and how does it control workload?Senior
  81. 81What is cross-database ownership chaining and its security risks?Senior
  82. 82What is SQL Server Service Principal Name (SPN) and Kerberos authentication?Senior
  83. 83What is index maintenance strategy in large-scale SQL Server systems?Senior
  84. 84What is optimistic vs pessimistic concurrency control in SQL Server?Senior
  85. 85What is SQL Server FILESTREAM and when should it be used?Senior
  86. 86What is database checkpoint and how does it improve recovery performance?Senior
  87. 87What is SQL Server recovery model and how does it affect backups?Senior
  88. 88What is SQL Server Transaction Log architecture and how does write-ahead logging work?Senior
  89. 89What is online index rebuild and how does it work internally?Senior
  90. 90What is filtered statistics and why are they useful?Senior
  91. 91What is execution plan skew in parallel queries?Senior
  92. 92What is PFS, GAM, and SGAM pages in tempdb architecture?Senior
  93. 93What is column elimination and row group elimination in columnstore indexes?Senior
  94. 94What is execution plan caching and plan reuse behavior in SQL Server?Senior
  95. 95What is interleaved execution in SQL Server?Senior
  96. 96What is query memory grant feedback in SQL Server?Senior
  97. 97What is index fragmentation and how does it affect query performance?Senior
  98. 98What is SQL Server latch vs spinlock vs lock, and how are they different internally?Senior
  99. 99What is automatic tuning in SQL Server?Senior
  100. 100What is SQL Server memory pressure and how do you detect it?Senior
  101. 101What are indexed views and how do they work internally?Senior
  102. 102What is schema binding in SQL Server views and functions?Senior
  103. 103What is Fill Factor in indexes and how does it impact performance?Senior
  104. 104What is parallel query execution and how does SQL Server decide to parallelize?Senior
  105. 105What is latch contention in SQL Server?Senior
  106. 106What is a bitmap filter in SQL Server execution plans?Senior
  107. 107What are computed columns and how do they affect indexing?Senior
  108. 108What is SARGability and why does it matter for performance?Senior
  109. 109What is index seek vs index scan vs key lookup in SQL Server?Senior
  110. 110What is MERGE statement and why is it controversial?Senior
  111. 111What is statistics histogram density and how is it used?Senior
  112. 112What is SQL Server thread and scheduler architecture?Senior
  113. 113What is SQL injection and how does SQL Server prevent it?Senior
  114. 114What is adaptive query processing in SQL Server?Senior
  115. 115What are memory grants and memory spills in execution plans?Senior
  116. 116What is tempdb contention and how do you resolve it?Senior
  117. 117What is dynamic SQL and what are its risks?Senior
  118. 118What is execution context switching in SQL Server?Senior
  119. 119What is blocking vs deadlocking in SQL Server?Senior
  120. 120How does SQL Server buffer pool management work?Senior
  121. 121What is query plan regression and how do you fix it?Senior
  122. 122What is Cardinality Estimation in SQL Server and why does it matter?Senior
  123. 123What is JSON support in SQL Server and how is it used?Senior
  124. 124What is plan cache and how do you manage it?Senior
  125. 125What is SQL Server Service Broker?Senior
  126. 126What are filtered indexes and when should they be used?Senior
  127. 127What is the difference between logical and physical reads?Senior
  128. 128What is SQL Server locking hierarchy?Senior
  129. 129What is CDC (Change Data Capture) in SQL Server?Senior
  130. 130What is temporal table in SQL Server?Senior
  131. 131What is Query Store in SQL Server?Senior
  132. 132What are memory-optimized tables in SQL Server?Senior
  133. 133What is SQL Server replication and its types?Senior
  134. 134What is Always On Availability Groups in SQL Server?Senior
  135. 135What is Columnstore index and when should it be used?Senior
  136. 136What is partitioning in SQL Server and when should you use it?Senior
  137. 137What are SQL Server statistics and why are they critical for performance?Senior
  138. 138What is a CTE in SQL Server?Senior
  139. 139T-SQL Advanced Interview Question 10Beginner
  140. 140T-SQL Advanced Interview Question 9Senior
  141. 141T-SQL Advanced Interview Question 8Intermediate
  142. 142T-SQL Advanced Interview Question 7Beginner
  143. 143T-SQL Advanced Interview Question 6Senior

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Frequently asked questions

Are these T-SQL interview questions up to date for 2026?

Yes. This page reflects 143 T-SQL interview questions kept current with today's frameworks, tooling and interview trends, with each answer maintained and dated.

What T-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.