Calculate the cumulative distribution of employee salaries.

Problem Statement

<p>Calculate the cumulative distribution of employee salaries.</p>

Examples

Input: employees table: +----+---------+--------+ | id | name | salary | +----+---------+--------+ | 1 | Alice | 50000 | | 2 | Bob | 60000 | | 3 | Charlie | 70000 | | 4 | Dana | 80000 | | 5 | Eve | 90000 | +----+---------+--------+

Output: +---------+--------+-----------+ | name | salary | cume_dist | +---------+--------+-----------+ | Alice | 50000 | 0.20 | | Bob | 60000 | 0.40 | | Charlie | 70000 | 0.60 | | Dana | 80000 | 0.80 | | Eve | 90000 | 1.00 | +---------+--------+-----------+

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 "Cumulative Distribution (CUME_DIST)", we query the relational database engine using declarative SQL. The goal is to calculate the cumulative distribution of employee salaries. 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 row projections to isolate the requested data.
Format & Order: Sort the resulting records according to specified order criteria.

Optimal Implementation (SQL)

SELECT name, salary, ROUND(CUME_DIST() OVER (ORDER BY salary)::NUMERIC, 2) AS cume_dist FROM employees;

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.

Cumulative Distribution (CUME_DIST)

Hard

Calculate the cumulative distribution of employee salaries.

Example Scenarios

1Example 1

Input:

employees table

id	name	salary
1	Alice	50000
2	Bob	60000
3	Charlie	70000
4	Dana	80000
5	Eve	90000

Output:

name	salary	cume_dist
Alice	50000	0.20
Bob	60000	0.40
Charlie	70000	0.60
Dana	80000	0.80
Eve	90000	1.00

Explanation:

The query retrieves the requested records satisfying all problem requirements.

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Query Results

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