Select user name, and replace NULL age with 0 using COALESCE.

Problem Statement

<p>Select user name, and replace NULL age with 0 using COALESCE.</p>

Examples

Input: users table: +----+-------+------+ | id | name | age | +----+-------+------+ | 1 | Alice | 30 | | 2 | Bob | NULL | +----+-------+------+

Output: +-------+----------+ | name | coalesce | +-------+----------+ | Alice | 30 | | Bob | 0 | +-------+----------+

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

Complexity

Time Complexity: -

Space Complexity: -

Hints

💡 Hint 1: Carefully review the required fields in the table schema. 💡 Hint 2: Construct a clean SELECT statement specifying the requested columns or wildcard *. 💡 Hint 3: Structure: SELECT <columns> FROM <table_name>;

Editorial & Approach

Problem Overview & Intuition

To solve "COALESCE Function", we query the relational database engine using declarative SQL. The goal is to select user name, and replace null age with 0 using coalesce. 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, COALESCE(age, 0) FROM users;

Complexity Analysis

Time Complexity O(N)

Space Complexity O(1)

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.

COALESCE Function

Easy

Select user name, and replace NULL age with 0 using COALESCE.

Example Scenarios

1Example 1

Input:

users table

id	name	age
1	Alice	30
2	Bob	NULL

Output:

name	coalesce
Alice	30
Bob	0

Explanation:

The query retrieves the requested records satisfying all problem requirements.

SQL Editor

Loading Editor...

Query Results

Run a query to see results here.