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Home/Questions/Python/Coding/List every combination of dept_name, employee_name, and city such that the employee belongs to the department and the same city in which the department is located.

List every combination of dept_name, employee_name, and city such that the employee belongs to the department and the same city in which the department is located.

Python/Codingmedium0.6 min readPremium

**Why Join + Same-Location Filter:** Business rule: employee must be in dept AND colocated. The join condition e.city = d.city enforces referential locality—critical for org hierarchy and location-based access control. **Query Design:** JOIN on dept_id plus e.city = d.city....

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Frequency
Low
Asked at 1 company
Category
179
questions in Python/Coding
Difficulty Split
127E|24M|28H
in this category
Total Bank
1,863
across 7 categories
Asked at these companies
Freight Tiger
Key Concepts Tested
join

Why This Question Matters

This medium-level Python/Coding question appears frequently in data engineering interviews at companies like Freight Tiger. While less common, it tests deeper understanding that distinguishes strong candidates. Mastering the underlying concepts (join) will help you answer variations of this question confidently.

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Break this problem into components. Identify the core trade-offs involved, then walk the interviewer through your reasoning step by step. Demonstrate awareness of edge cases and production considerations - this is what separates good answers from great ones.

Expert Answer
112 words

Why Join + Same-Location Filter: Business rule: employee must be in dept AND colocated. The join condition e.city = d.city enforces referential locality—critical for org hierarchy and location-based access control.

Query Design: JOIN on dept_id plus e.city = d.city. Alternative: JOIN on (dept_id, city) as composite key if indexed—can be faster. Use INNER JOIN when you want only matching pairs; LEFT JOIN if you need depts with no local employees (would show NULL).

Scalability: Index (dept_id, city) on both tables. For large orgs (100K+ employees): consider materialized view for 'employees by location' refreshed nightly.

SELECT d.dept_name, e.employee_name, e.city
FROM employees e
JOIN departments d ON e.dept_id = d.dept_id AND e.city = d.city;

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According to DataEngPrep.tech, this is one of the most frequently asked Python/Coding interview questions, reported at 1 company. DataEngPrep.tech maintains a curated database of 1,863+ real data engineering interview questions across 7 categories, verified by industry professionals.

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