SQL interview questions

Review short answers, detailed answers, practical code and common mistakes.

1. How would you explain SQL Introduction in SQL during an interview?beginner

SQL Introduction is best explained with its purpose, a small example, and one common mistake.

Start by naming the problem sql introduction solves in SQL. Then show a short example, discuss the tradeoff, and mention how you would test it in a real codebase.

SELECT customer, total, status
FROM orders
WHERE total >= 50
ORDER BY total DESC;

2. How would you explain SELECT in SQL during an interview?beginner

SELECT is best explained with its purpose, a small example, and one common mistake.

Start by naming the problem select solves in SQL. Then show a short example, discuss the tradeoff, and mention how you would test it in a real codebase.

3. How would you explain WHERE in SQL during an interview?beginner

WHERE is best explained with its purpose, a small example, and one common mistake.

Start by naming the problem where solves in SQL. Then show a short example, discuss the tradeoff, and mention how you would test it in a real codebase.

4. How would you explain ORDER BY in SQL during an interview?beginner

ORDER BY is best explained with its purpose, a small example, and one common mistake.

Start by naming the problem order by solves in SQL. Then show a short example, discuss the tradeoff, and mention how you would test it in a real codebase.

SELECT customer, total, status
FROM orders
WHERE total >= 53
ORDER BY total DESC;

5. How would you explain LIMIT in SQL during an interview?beginner

LIMIT is best explained with its purpose, a small example, and one common mistake.

Start by naming the problem limit solves in SQL. Then show a short example, discuss the tradeoff, and mention how you would test it in a real codebase.

6. How would you explain INSERT in SQL during an interview?beginner

INSERT is best explained with its purpose, a small example, and one common mistake.

Start by naming the problem insert solves in SQL. Then show a short example, discuss the tradeoff, and mention how you would test it in a real codebase.

7. How would you explain UPDATE in SQL during an interview?beginner

UPDATE is best explained with its purpose, a small example, and one common mistake.

Start by naming the problem update solves in SQL. Then show a short example, discuss the tradeoff, and mention how you would test it in a real codebase.

UPDATE orders
SET status = 'refunded'
WHERE id = 42 AND status = 'paid';

8. How would you explain DELETE in SQL during an interview?beginner

DELETE is best explained with its purpose, a small example, and one common mistake.

Start by naming the problem delete solves in SQL. Then show a short example, discuss the tradeoff, and mention how you would test it in a real codebase.

9. How would you explain GROUP BY in SQL during an interview?beginner

GROUP BY is best explained with its purpose, a small example, and one common mistake.

Start by naming the problem group by solves in SQL. Then show a short example, discuss the tradeoff, and mention how you would test it in a real codebase.

10. How would you explain HAVING in SQL during an interview?beginner

HAVING is best explained with its purpose, a small example, and one common mistake.

Start by naming the problem having solves in SQL. Then show a short example, discuss the tradeoff, and mention how you would test it in a real codebase.

SELECT status, COUNT(*) AS orders, SUM(total) AS revenue
FROM orders
GROUP BY status
HAVING SUM(total) >= 59;

11. How would you explain JOIN in SQL during an interview?intermediate

JOIN is best explained with its purpose, a small example, and one common mistake.

Start by naming the problem join solves in SQL. Then show a short example, discuss the tradeoff, and mention how you would test it in a real codebase.

12. How would you explain Subqueries in SQL during an interview?intermediate

Subqueries is best explained with its purpose, a small example, and one common mistake.

Start by naming the problem subqueries solves in SQL. Then show a short example, discuss the tradeoff, and mention how you would test it in a real codebase.

13. How would you explain Constraints in SQL during an interview?intermediate

Constraints is best explained with its purpose, a small example, and one common mistake.

Start by naming the problem constraints solves in SQL. Then show a short example, discuss the tradeoff, and mention how you would test it in a real codebase.

SELECT customer, total, status
FROM orders
WHERE total >= 62
ORDER BY total DESC;

14. How would you explain Views in SQL during an interview?intermediate

Views is best explained with its purpose, a small example, and one common mistake.

Start by naming the problem views solves in SQL. Then show a short example, discuss the tradeoff, and mention how you would test it in a real codebase.

15. How would you explain Indexes in SQL during an interview?intermediate

Indexes is best explained with its purpose, a small example, and one common mistake.

Start by naming the problem indexes solves in SQL. Then show a short example, discuss the tradeoff, and mention how you would test it in a real codebase.

16. How would you explain Transactions in SQL during an interview?intermediate

Transactions is best explained with its purpose, a small example, and one common mistake.

Start by naming the problem transactions solves in SQL. Then show a short example, discuss the tradeoff, and mention how you would test it in a real codebase.

SELECT customer, total, status
FROM orders
WHERE total >= 65
ORDER BY total DESC;

17. How would you explain Stored Procedures in SQL during an interview?intermediate

Stored Procedures is best explained with its purpose, a small example, and one common mistake.

Start by naming the problem stored procedures solves in SQL. Then show a short example, discuss the tradeoff, and mention how you would test it in a real codebase.

18. How would you explain Query Optimization in SQL during an interview?intermediate

Query Optimization is best explained with its purpose, a small example, and one common mistake.

Start by naming the problem query optimization solves in SQL. Then show a short example, discuss the tradeoff, and mention how you would test it in a real codebase.

19. How would you explain Database Project in SQL during an interview?intermediate

Database Project is best explained with its purpose, a small example, and one common mistake.

Start by naming the problem database project solves in SQL. Then show a short example, discuss the tradeoff, and mention how you would test it in a real codebase.

SELECT customer, total, status
FROM orders
WHERE total >= 68
ORDER BY total DESC;

20. How would you explain Data Types in SQL during an interview?intermediate

Data Types is best explained with its purpose, a small example, and one common mistake.

Start by naming the problem data types solves in SQL. Then show a short example, discuss the tradeoff, and mention how you would test it in a real codebase.

21. How would you explain Aggregates in SQL during an interview?advanced

Aggregates is best explained with its purpose, a small example, and one common mistake.

Start by naming the problem aggregates solves in SQL. Then show a short example, discuss the tradeoff, and mention how you would test it in a real codebase.

22. How would you explain Aliases in SQL during an interview?advanced

Aliases is best explained with its purpose, a small example, and one common mistake.

Start by naming the problem aliases solves in SQL. Then show a short example, discuss the tradeoff, and mention how you would test it in a real codebase.

SELECT customer, total, status
FROM orders
WHERE total >= 71
ORDER BY total DESC;

23. How would you explain NULL Handling in SQL during an interview?advanced

NULL Handling is best explained with its purpose, a small example, and one common mistake.

Start by naming the problem null handling solves in SQL. Then show a short example, discuss the tradeoff, and mention how you would test it in a real codebase.

24. How would you explain CASE Expressions in SQL during an interview?advanced

CASE Expressions is best explained with its purpose, a small example, and one common mistake.

Start by naming the problem case expressions solves in SQL. Then show a short example, discuss the tradeoff, and mention how you would test it in a real codebase.

25. How would you explain Relationships in SQL during an interview?advanced

Relationships is best explained with its purpose, a small example, and one common mistake.

Start by naming the problem relationships solves in SQL. Then show a short example, discuss the tradeoff, and mention how you would test it in a real codebase.

SELECT customer, total, status
FROM orders
WHERE total >= 74
ORDER BY total DESC;

26. How would you explain ER Diagrams in SQL during an interview?advanced

ER Diagrams is best explained with its purpose, a small example, and one common mistake.

Start by naming the problem er diagrams solves in SQL. Then show a short example, discuss the tradeoff, and mention how you would test it in a real codebase.

27. How would you explain Security Basics in SQL during an interview?advanced

Security Basics is best explained with its purpose, a small example, and one common mistake.

Start by naming the problem security basics solves in SQL. Then show a short example, discuss the tradeoff, and mention how you would test it in a real codebase.

28. How would you explain Backup Basics in SQL during an interview?advanced

Backup Basics is best explained with its purpose, a small example, and one common mistake.

Start by naming the problem backup basics solves in SQL. Then show a short example, discuss the tradeoff, and mention how you would test it in a real codebase.

SELECT customer, total, status
FROM orders
WHERE total >= 77
ORDER BY total DESC;

29. How would you explain Reporting Queries in SQL during an interview?advanced

Reporting Queries is best explained with its purpose, a small example, and one common mistake.

Start by naming the problem reporting queries solves in SQL. Then show a short example, discuss the tradeoff, and mention how you would test it in a real codebase.

30. How would you explain SQL Review in SQL during an interview?advanced

SQL Review is best explained with its purpose, a small example, and one common mistake.

Start by naming the problem sql review solves in SQL. Then show a short example, discuss the tradeoff, and mention how you would test it in a real codebase.