Find users older than the average age.

Problem Statement

<p>Find <code>users</code> older than the average age.</p>

Examples

Input: users table: +----+---------+-----+ | id | name | age | +----+---------+-----+ | 1 | Alice | 20 | | 2 | Bob | 30 | | 3 | Charlie | 40 | +----+---------+-----+

Output: +----+---------+-----+ | id | name | age | +----+---------+-----+ | 3 | Charlie | 40 | +----+---------+-----+

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

Complexity

Time Complexity: -

Space Complexity: -

Hints

💡 Hint 1: Identify the filtering conditions needed to isolate the target rows from the table. 💡 Hint 2: Use appropriate operators: = for exact matches, LIKE for wildcard patterns, IN for sets, or BETWEEN for numeric/date ranges. 💡 Hint 3: Combine filters with AND/OR if multiple conditions exist: SELECT <cols> FROM <table> WHERE <condition>;

Editorial & Approach

Problem Overview & Intuition

To solve "Subquery in WHERE", we query the relational database engine using declarative SQL. The goal is to find users older than the average age. 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: Ensure columns match the expected project schema in order.

Optimal Implementation (SQL)

SELECT * FROM users WHERE age > (SELECT AVG(age) FROM users);

Complexity Analysis

Time Complexity O(N) full table scan or O(log N) if filtered column is indexed.

Space Complexity O(K) where K is the number of filtered rows returned.

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.

Subquery in WHERE

Medium

Find users older than the average age.

Example Scenarios

1Example 1

Input:

users table

id	name	age
1	Alice	20
2	Bob	30
3	Charlie	40

Output:

id	name	age
3	Charlie	40

Explanation:

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

SQL Editor

Loading Editor...

Query Results

Run a query to see results here.