For each department, concatenate all employee names separated by commas.

Problem Statement

<p>For each department, concatenate all employee names separated by commas.</p>

Examples

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

Output: +------------+---------------+ | department | team_members | +------------+---------------+ | HR | Charlie, Dana | | IT | Alice, Bob | +------------+---------------+

Explanation: Only records matching the specified criteria are returned in the final result.

Complexity

Time Complexity: -

Space Complexity: -

Hints

💡 Hint 1: Identify the grouping dimension(s) and which columns require aggregate functions (such as COUNT, SUM, AVG, MIN, or MAX). 💡 Hint 2: Add the GROUP BY clause for all non-aggregated columns listed in the SELECT projection. 💡 Hint 3: If filtering groups, use HAVING; otherwise use WHERE before grouping: SELECT <group_col>, <AGG>(...) FROM <table> GROUP BY <group_col>;

Editorial & Approach

Problem Overview & Intuition

To solve "STRING_AGG Function", we query the relational database engine using declarative SQL. The goal is to for each department, concatenate all employee names separated by commas. 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 grouping & aggregates to isolate the requested data.
Format & Order: Sort the resulting records according to specified order criteria.

Optimal Implementation (SQL)

SELECT department, STRING_AGG(name, ', ' ORDER BY name) AS team_members FROM employees GROUP BY department;

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.

STRING_AGG Function

Medium

For each department, concatenate all employee names separated by commas.

Example Scenarios

1Example 1

Input:

employees table

id	name	department
1	Alice	IT
2	Bob	IT
3	Charlie	HR
4	Dana	HR

Output:

department	team_members
HR	Charlie, Dana
IT	Alice, Bob

Explanation:

Only records matching the specified criteria are returned in the final result.

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