Sort `employees` by `department` ascending, then by `salary` descending.

Problem Statement

<p>Sort <code>employees</code> by <code>department</code> ascending, then by <code>salary</code> descending.</p>

Examples

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

Output: +----+---------+------------+--------+ | id | name | department | salary | +----+---------+------------+--------+ | 4 | Dana | HR | 75000 | | 2 | Bob | HR | 60000 | | 3 | Charlie | IT | 120000 | | 1 | Alice | IT | 90000 | +----+---------+------------+--------+

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

Complexity

Time Complexity: -

Space Complexity: -

Hints

💡 Hint 1: Determine the sort order (ASC for ascending, DESC for descending) and whether only top records are required. 💡 Hint 2: Specify ORDER BY <column> [ASC|DESC] and append LIMIT <n> to cap the result set. 💡 Hint 3: Assemble: SELECT <cols> FROM <table> ORDER BY <col> [DESC] LIMIT <n>;

Editorial & Approach

Problem Overview & Intuition

To solve "Multi-Column ORDER BY", we query the relational database engine using declarative SQL. The goal is to sort `employees` by `department` ascending, then by `salary` descending. 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 * FROM employees ORDER BY department ASC, salary DESC;

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.

Multi-Column ORDER BY

Easy

Sort employees by department ascending, then by salary descending.

Example Scenarios

1Example 1

Input:

employees table

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

Output:

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

Explanation:

The query retrieves the requested records satisfying all problem requirements.

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