Show each employee salary as a percentage of the total salary bill.

Problem Statement

<p>Show each employee salary as a percentage of the total salary bill.</p>

Examples

Input: employees table: +----+---------+--------+ | id | name | salary | +----+---------+--------+ | 1 | Alice | 50000 | | 2 | Bob | 30000 | | 3 | Charlie | 20000 | +----+---------+--------+

Output: +---------+--------+--------------+ | name | salary | pct_of_total | +---------+--------+--------------+ | Alice | 50000 | 50.00 | | Bob | 30000 | 30.00 | | Charlie | 20000 | 20.00 | +---------+--------+--------------+

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 "Percent of Total", we query the relational database engine using declarative SQL. The goal is to show each employee salary as a percentage of the total salary bill. 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: Ensure columns match the expected project schema in order.

Optimal Implementation (SQL)

SELECT name, salary, ROUND(salary * 100.0 / SUM(salary) OVER (), 2) AS pct_of_total 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.

Percent of Total

Hard

Show each employee salary as a percentage of the total salary bill.

Example Scenarios

1Example 1

Input:

employees table

id	name	salary
1	Alice	50000
2	Bob	30000
3	Charlie	20000

Output:

name	salary	pct_of_total
Alice	50000	50.00
Bob	30000	30.00
Charlie	20000	20.00

Explanation:

The query retrieves the requested records satisfying all problem requirements.

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