Find the name, department, and salary of the highest paid employee in each department.

Problem Statement

<p>Find the name, department, and salary of the highest paid employee in each department.</p>

Examples

Input: employees table: +----+---------+------------+--------+ | id | name | department | salary | +----+---------+------------+--------+ | 1 | Alice | IT | 90000 | | 2 | Bob | IT | 120000 | | 3 | Charlie | HR | 60000 | | 4 | Dana | HR | 75000 | | 5 | Eve | Sales | 80000 | +----+---------+------------+--------+

Output: +------+------------+--------+ | name | department | salary | +------+------------+--------+ | Dana | HR | 75000 | | Bob | IT | 120000 | | Eve | Sales | 80000 | +------+------------+--------+

Explanation: The query retrieves the requested records satisfying all problem requirements.

Complexity

Time Complexity: -

Space Complexity: -

Hints

💡 Hint 1: Use a window function with OVER (...) to compute values across rows related to the current row without collapsing them like GROUP BY. 💡 Hint 2: Check if PARTITION BY is required to split windows by category or if only an ORDER BY inside OVER (...) is needed. 💡 Hint 3: Structure the query as: <window_func>() OVER (PARTITION BY ... ORDER BY ...) AS <alias>;

Editorial & Approach

Problem Overview & Intuition

To solve "Highest Paid in Each Department", we query the relational database engine using declarative SQL. The goal is to find the name, department, and salary of the highest paid employee in each department. By formulating an optimal execution plan with appropriate projection and filtering, the database engine executes the query with minimal overhead.

Step-by-Step Approach

Analyze Schema: Identify the target tables, necessary foreign keys, and expected output columns.
Construct Filtering & Logic: Apply WHERE filtering to isolate the requested data.
Format & Order: Sort the resulting records according to specified order criteria.

Optimal Implementation (SQL)

SELECT name, department, salary FROM (SELECT name, department, salary, RANK() OVER (PARTITION BY department ORDER BY salary DESC) AS rk FROM employees) sub WHERE rk = 1;

Complexity Analysis

Time Complexity O(N log N) for sorting or partitioning rows.

Space Complexity O(N) for intermediate group hash tables or window buffers.

Key Considerations & Edge Cases

Empty Tables: The query executes safely returning zero rows without syntax error.
NULL Values: Columns containing NULL values are properly handled by standard ANSI SQL semantics.
Case Sensitivity: String comparisons and keywords adhere to PostgreSQL/standard SQL rules.

Highest Paid in Each Department

Hard

Find the name, department, and salary of the highest paid employee in each department.

Example Scenarios

1Example 1

Input:

employees table

id	name	department	salary
1	Alice	IT	90000
2	Bob	IT	120000
3	Charlie	HR	60000
4	Dana	HR	75000
5	Eve	Sales	80000

Output:

name	department	salary
Dana	HR	75000
Bob	IT	120000
Eve	Sales	80000

Explanation:

The query retrieves the requested records satisfying all problem requirements.

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