𝗜𝗻𝘁𝗲𝗿𝘃𝗶𝗲𝘄𝗲𝗿:
You have 2 minutes to solve this SQL query.

Find employees who earn the same salary as at least one other employee in the same department.

𝗠𝗲: Challenge accepted! 💪
SELECT
employee_id,
employee_name,
department,
salary
FROM employees
WHERE (department, salary) IN (
SELECT
department,
salary
FROM employees
GROUP BY department, salary
HAVING COUNT(*) > 1
)
ORDER BY department, salary DESC;

💡 Explanation:
The query identifies duplicate salary values within each department.

• The subquery groups records by department and salary.
• **HAVING COUNT(*) > 1** finds salary values that appear more than once in the same department.
• The outer query returns all employees whose (department, salary) matches those duplicate combinations.

This question tests your understanding of:
✅ GROUP BY
✅ HAVING
✅ Multi-column filtering
✅ Identifying duplicate records

🎯 Expected Output Example
Employee Department Salary
John IT 80,000
Alice IT 80,000
David HR 65,000
Sarah HR 65,000

🚀 Alternative Using Window Functions
SELECT
employee_id,
employee_name,
department,
salary
FROM (
SELECT
*,
COUNT(*) OVER (
PARTITION BY department, salary
) AS salary_count
FROM employees
) t
WHERE salary_count > 1;

This approach avoids a subquery with GROUP BY and is a great way to showcase your knowledge of window functions.

🚀 When interview questions ask you to find duplicates, think of these three approaches:

1. GROUP BY + HAVING
2. Window functions COUNT() OVER
3. Self Join for specific comparison scenarios

Knowing multiple solutions demonstrates strong SQL problem-solving skills.

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