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Section 1 — SQL Basics & Queries

Questions 1–10

10 Qs

01What is SQL? Differentiate between DDL, DML, DCL, and TCL with examples.Basic

02Write a SQL query to retrieve all columns from a table called employees where salary is greater than 50,000.Basic

03What is the difference between WHERE and HAVING clauses? When is each used?Basic

04Explain GROUP BY with an example. How does it work with aggregate functions?Basic

05What is the difference between DELETE, TRUNCATE, and DROP?Basic

06What are aggregate functions? Name five and explain their usage.Basic

07How does the ORDER BY clause work? Can you order by multiple columns?Basic

08What is a subquery? Write an example of a correlated vs non-correlated subquery.Medium

09Explain DISTINCT, LIMIT, and OFFSET in SQL with use-cases.Basic

10What is the difference between UNION and UNION ALL? When would you choose one over the other?Medium

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Section 2 — Joins & Relationships

Questions 11–20

10 Qs

11What are the different types of SQL JOINs? Explain each with a diagram description.Basic

12What is an INNER JOIN? Write a query joining orders and customers on customer_id.Basic

13Explain LEFT JOIN vs RIGHT JOIN. What happens when there is no matching row on the outer side?Basic

14What is a FULL OUTER JOIN and when would you use it? Is it supported in MySQL?Medium

15What is a CROSS JOIN? Give a practical use-case where it makes sense.Medium

16What is a SELF JOIN? Write an example query to find employees who have the same manager.Medium

17What is the difference between a Primary Key and a Foreign Key? Can a table have multiple foreign keys?Basic

18What is referential integrity? How do ON DELETE CASCADE and ON UPDATE CASCADE work?Medium

19How do you retrieve the second-highest salary from an employees table? Write multiple approaches.Medium

20Write a query to find all customers who have NOT placed any orders (using both LEFT JOIN and NOT EXISTS).Medium

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Section 3 — Normalization & Database Design

Questions 21–30

10 Qs

21What is database normalization? Why is it important in relational database design?Basic

22Explain First Normal Form (1NF). What problem does it solve? Give a before/after example.Basic

23What is Second Normal Form (2NF)? Explain partial dependency with an example.Medium

24What is Third Normal Form (3NF)? How does transitive dependency violate 3NF?Medium

25What is Boyce-Codd Normal Form (BCNF)? How does it differ from 3NF?Advanced

26What is denormalization? When would you intentionally denormalize a database?Medium

27What is an Entity-Relationship (ER) diagram? Explain entities, attributes, and relationships.Basic

28What are the different types of relationships in database design? (1:1, 1:N, M:N) Give real-world examples.Basic

29What is a composite key? When should you use it instead of a surrogate key?Medium

30What is a candidate key vs a super key? Explain with a table example.Medium

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Section 4 — Indexing & Performance

Questions 31–38

8 Qs

31What is a database index? How does it improve query performance?Basic

32What is the difference between a Clustered and a Non-Clustered index?Medium

33What is a composite index? When should you use one and how does column order matter?Medium

34What are the downsides of indexing? Why shouldn't you index every column?Medium

35What is a covering index? How can it eliminate table lookups?Advanced

36What is EXPLAIN / EXPLAIN ANALYZE? How do you use it to diagnose slow queries?Medium

37What is query optimization? List five best practices for writing performant SQL.Medium

38What is database partitioning? Explain horizontal vs vertical partitioning and sharding.Advanced

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Section 5 — Transactions & ACID Properties

Questions 39–46

8 Qs

39What is a database transaction? Explain COMMIT, ROLLBACK, and SAVEPOINT.Basic

40What are ACID properties? Explain each: Atomicity, Consistency, Isolation, Durability.Basic

41What are transaction isolation levels in SQL? Explain READ UNCOMMITTED, READ COMMITTED, REPEATABLE READ, and SERIALIZABLE.Medium

42What is a Dirty Read, Non-Repeatable Read, and Phantom Read? Which isolation levels prevent each?Medium

43What is a deadlock in a database? How can it be detected and prevented?Advanced

44What is optimistic vs pessimistic locking? When would you use each?Advanced

45What is a two-phase commit (2PC)? How does it ensure consistency in distributed transactions?Advanced

46What is Write-Ahead Logging (WAL)? How does it contribute to database durability?Advanced

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Section 6 — Stored Procedures, Views & Triggers

Questions 47–56

10 Qs

47What is a View in SQL? How do you create one and what are its advantages?Basic

48What is the difference between a simple view and a complex view? Can you update data through a view?Medium

49What is a Stored Procedure? How does it differ from a function in SQL?Basic

50Write a stored procedure that accepts an employee ID and returns their department name and salary.Medium

51What are the advantages of stored procedures? (Security, performance, reusability)Medium

52What is a Trigger in SQL? Explain BEFORE and AFTER triggers with an example.Medium

53What is a user-defined function (UDF)? What is the difference between scalar and table-valued functions?Medium

54What is a Cursor in SQL? When should you use one and what are the performance concerns?Advanced

55What are Materialized Views? How do they differ from regular views and when are they useful?Advanced

56What is a sequence / auto-increment? How is it used to generate primary keys?Basic

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Section 7 — Advanced SQL

Questions 57–66

10 Qs

57What are Window Functions? Explain ROW_NUMBER(), RANK(), and DENSE_RANK() with examples.Advanced

58What is PARTITION BY in window functions? How does it differ from GROUP BY?Advanced

59What is a CTE (Common Table Expression)? Write an example using WITH. How does it differ from a subquery?Medium

60What is a Recursive CTE? Write a query to traverse a hierarchical employee-manager table.Advanced

61What is CASE WHEN in SQL? Write a query that categorises employees by salary bracket.Medium

62What is PIVOT and UNPIVOT in SQL? Give a real-world use-case.Advanced

63What are LEAD() and LAG() window functions? Write a query showing month-over-month sales change.Advanced

64What is the difference between EXISTS and IN? Which is more performant and why?Medium

65How do you handle NULL values in SQL? Explain IS NULL, COALESCE(), and NULLIF().Medium

66What is a temporal table (system-versioned table)? How is it used for historical data tracking?Advanced

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Section 8 — NoSQL Databases

Questions 67–76

10 Qs

67What is NoSQL? How does it differ from relational databases? When would you choose NoSQL?Basic

68What are the four main types of NoSQL databases? (Document, Key-Value, Column-Family, Graph) — give an example of each.Basic

69What is MongoDB? Explain collections, documents, and BSON. How do you perform a basic CRUD operation?Basic

70What is the CAP theorem? Explain Consistency, Availability, and Partition Tolerance with examples.Medium

71What is eventual consistency in NoSQL systems? How does it trade off with strong consistency?Medium

72What is Redis? What data structures does it support and what are its common use-cases?Medium

73What is Cassandra? Explain its wide-column model, partition key, and clustering columns.Advanced

74What is a graph database? How does Neo4j represent data and when would you use it over a relational DB?Medium

75What is Elasticsearch? How does it index documents and what are its primary use-cases?Medium

76How do you choose between SQL and NoSQL for a new project? What factors drive that decision?Medium

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Section 9 — Cloud & Modern Databases

Questions 77–85

9 Qs

77What are managed cloud database services? Compare AWS RDS, Azure SQL Database, and Google Cloud SQL.Medium

78What is Amazon DynamoDB? Explain its key-value and document model, and its pricing model.Medium

79What is a Data Warehouse? How does it differ from an OLTP database? Give examples (Snowflake, Redshift).Medium

80What is OLTP vs OLAP? How do their schema designs (star schema, snowflake schema) differ?Medium

81What is a Data Lake? How does it differ from a Data Warehouse and when would you use each?Medium

82What is database replication? Explain master-slave (primary-replica) replication and its benefits.Advanced

83What is database caching? Explain how caching layers (Redis, Memcached) reduce DB load.Medium

84What is a NewSQL database? Name examples and explain how they combine SQL features with NoSQL scalability.Advanced

85What is database migration? What tools and strategies are used for zero-downtime schema changes in production?Advanced

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SQL & Databases
Question Set

9 Key SQL & Database Areas

All 85+ Questions

Section 1 — SQL Basics & Queries

Section 2 — Joins & Relationships

Section 3 — Normalization & Database Design

Section 4 — Indexing & Performance

Section 5 — Transactions & ACID Properties

Section 6 — Stored Procedures, Views & Triggers

Section 7 — Advanced SQL

Section 8 — NoSQL Databases

Section 9 — Cloud & Modern Databases

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SQL & Databases Question Set

9 Key SQL & Database Areas

All 85+ Questions

Section 1 — SQL Basics & Queries

Section 2 — Joins & Relationships

Section 3 — Normalization & Database Design

Section 4 — Indexing & Performance

Section 5 — Transactions & ACID Properties

Section 6 — Stored Procedures, Views & Triggers

Section 7 — Advanced SQL

Section 8 — NoSQL Databases

Section 9 — Cloud & Modern Databases

Want all 85+ questions as a formatted PDF?

Explore Other Sets

Get the SQL & Databases PDF — Free

SQL & Databases
Question Set