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MySQL & SQL Interview Questions

Joins, indexing, transactions, MVCC, EXPLAIN, window functions, CTEs, replication, and query optimization.

JoinsIndexingTransactionsWindow FunctionsPerformanceAria-powered explanations
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16 Easy51 Medium33 Hard

Showing 1–20 of 100

#1What are the different types of SQL JOINs?

Easy
Querying

#2How does indexing work in MySQL (InnoDB)?

Medium
Indexing

#3What is a covering index?

Medium
Indexing

#4What are MySQL transaction isolation levels?

Hard
Transactions

#5What is MVCC (Multi-Version Concurrency Control) in InnoDB?

Hard
Transactions

#6How do you use EXPLAIN to analyze a query?

Medium
Performance

#7What are window functions in SQL?

Hard
Advanced SQL

#8What are CTEs (Common Table Expressions) and when should you use them?

Medium
Advanced SQL

#9What is the N+1 query problem and how do you fix it?

Medium
Performance

#10What is a deadlock in MySQL and how does it occur?

Medium
Transactions

#11What is the difference between DELETE, TRUNCATE, and DROP?

Easy
Querying

#12How do you optimize a slow MySQL query?

Hard
Performance

#13What is database normalization?

Medium
Schema Design

#14What is MySQL replication and how does it work?

Hard
Operations

#15What is partitioning in MySQL?

Hard
Schema Design

#16What is GROUP BY vs HAVING in SQL?

Easy
Querying

#17What is a stored procedure and when should you use it?

Medium
Advanced SQL

#18How does the InnoDB storage engine handle locking?

Hard
Transactions

#19What is the difference between UNION and UNION ALL?

Easy
Querying

#20How do you design a schema for a multi-tenant SaaS application?

Hard
Schema Design

Showing 1–20 of 100

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All 100 MySQL & SQL questions at a glance
  1. What are the different types of SQL JOINs?(Easy)
  2. How does indexing work in MySQL (InnoDB)?(Medium)
  3. What is a covering index?(Medium)
  4. What are MySQL transaction isolation levels?(Hard)
  5. What is MVCC (Multi-Version Concurrency Control) in InnoDB?(Hard)
  6. How do you use EXPLAIN to analyze a query?(Medium)
  7. What are window functions in SQL?(Hard)
  8. What are CTEs (Common Table Expressions) and when should you use them?(Medium)
  9. What is the N+1 query problem and how do you fix it?(Medium)
  10. What is a deadlock in MySQL and how does it occur?(Medium)
  11. What is the difference between DELETE, TRUNCATE, and DROP?(Easy)
  12. How do you optimize a slow MySQL query?(Hard)
  13. What is database normalization?(Medium)
  14. What is MySQL replication and how does it work?(Hard)
  15. What is partitioning in MySQL?(Hard)
  16. What is GROUP BY vs HAVING in SQL?(Easy)
  17. What is a stored procedure and when should you use it?(Medium)
  18. How does the InnoDB storage engine handle locking?(Hard)
  19. What is the difference between UNION and UNION ALL?(Easy)
  20. How do you design a schema for a multi-tenant SaaS application?(Hard)
  21. What is the difference between a clustered and a non-clustered index?(Medium)
  22. How does MySQL handle AUTO_INCREMENT?(Easy)
  23. What are covering indexes and how do they improve performance?(Medium)
  24. What is the EXPLAIN output and how do you read it?(Medium)
  25. What are database triggers and when should you avoid them?(Medium)
  26. What is a foreign key constraint and what are its performance implications?(Medium)
  27. What is the difference between CHAR and VARCHAR?(Easy)
  28. How do you implement full-text search in MySQL?(Medium)
  29. What is the difference between MyISAM and InnoDB?(Easy)
  30. How does MySQL replication work and what are its modes?(Hard)
  31. What is a deadlock in MySQL and how does InnoDB handle it?(Hard)
  32. What are MySQL stored procedures and when should you use them?(Medium)
  33. How do you perform a slow query analysis in MySQL?(Medium)
  34. What is InnoDB buffer pool and how do you size it?(Hard)
  35. What is the difference between HAVING and WHERE?(Easy)
  36. What is MySQL's query cache and why was it removed?(Medium)
  37. How do you back up a MySQL database without downtime?(Medium)
  38. What is the difference between optimistic and pessimistic locking in MySQL?(Medium)
  39. What are MySQL partitioning types and when do you use them?(Hard)
  40. How do you handle large data migrations in production?(Hard)
  41. What is the difference between IN, EXISTS, and JOIN for subqueries?(Medium)
  42. What is the InnoDB redo log and undo log?(Hard)
  43. How do you implement pagination in MySQL efficiently?(Medium)
  44. What are the different types of JOINs in MySQL?(Easy)
  45. What is group replication and InnoDB Cluster?(Hard)
  46. What is the difference between a view and a materialized view?(Medium)
  47. How does MySQL's optimizer choose an execution plan?(Hard)
  48. What are common MySQL performance anti-patterns?(Medium)
  49. What is a generated column in MySQL?(Medium)
  50. What are the best practices for MySQL schema design?(Medium)
  51. How do you use MySQL's JSON column type?(Medium)
  52. What is the difference between transaction isolation levels in MySQL?(Hard)
  53. How do you handle hierarchical data in MySQL?(Hard)
  54. What is ProxySQL and how is it used?(Medium)
  55. What is MVCC and how does InnoDB implement it?(Hard)
  56. How do you detect and fix index fragmentation in MySQL?(Medium)
  57. What are the MySQL 8.0 improvements over MySQL 5.7?(Medium)
  58. How do you design a schema for audit logging?(Medium)
  59. What is binlog and how is it used for CDC?(Hard)
  60. How do you use MySQL's performance_schema?(Hard)
  61. What is the difference between COUNT(*), COUNT(1), and COUNT(col)?(Easy)
  62. What is a composite index and how should you order columns?(Hard)
  63. How do you implement soft delete in MySQL?(Medium)
  64. What is the difference between CHAR, VARCHAR, TEXT, and BLOB?(Easy)
  65. How does MySQL handle concurrent writes to the same row?(Hard)
  66. What is the difference between schema-on-write and schema-on-read?(Medium)
  67. How do you handle time zones in MySQL?(Medium)
  68. What is the difference between a unique constraint and a unique index?(Easy)
  69. How do you monitor MySQL in production?(Medium)
  70. What are window functions and how do you use them?(Medium)
  71. How do you implement row-level security in MySQL?(Hard)
  72. What is the difference between a primary key and a unique key?(Easy)
  73. How do you use MySQL's event scheduler?(Medium)
  74. What is the EXPLAIN ANALYZE command?(Medium)
  75. How do you handle database connection failures in application code?(Medium)
  76. What is the MySQL query execution order?(Medium)
  77. How do you scale MySQL reads?(Medium)
  78. What is the difference between row-based and statement-based replication?(Medium)
  79. How do you use CTEs (Common Table Expressions) effectively?(Medium)
  80. What is the difference between TRUNCATE, DELETE, and DROP?(Easy)
  81. How do you implement optimistic locking with versioning in MySQL?(Medium)
  82. What are the different ways to copy a table in MySQL?(Easy)
  83. What is the purpose of the information_schema?(Medium)
  84. What is innodb_flush_log_at_trx_commit and how does it affect durability?(Hard)
  85. How do you implement full-table search across millions of rows efficiently?(Medium)
  86. What is the max_connections parameter and how do you tune it?(Medium)
  87. What is a spatial index in MySQL and how is it used?(Hard)
  88. What is the difference between ROLLUP and CUBE in SQL?(Medium)
  89. How do you handle NULL values in MySQL queries?(Medium)
  90. What is the difference between a read and a write transaction?(Medium)
  91. How do you implement a queue in MySQL?(Hard)
  92. What is the mysql.user table and how does MySQL authentication work?(Medium)
  93. What is index merge optimization?(Hard)
  94. How do you detect and resolve replication lag?(Hard)
  95. What is the difference between MyISAM and InnoDB row format?(Hard)
  96. How do you implement rate limiting at the database level?(Hard)
  97. What is the difference between REPEATABLE READ and READ COMMITTED in practice?(Hard)
  98. What are MySQL's data types for storing money?(Medium)
  99. How do you handle schema evolution in a microservices environment?(Hard)
  100. What is the difference between DATETIME and TIMESTAMP in MySQL?(Easy)