Concatenate the `first_name` and `last_name` columns with a space in between, aliased as `full_name`.

Problem Statement

<p>Concatenate the <code>first_name</code> and <code>last_name</code> columns with a space in between, aliased as <code>full_name</code>.</p>

Examples

Input: users table: +----+------------+-----------+ | id | first_name | last_name | +----+------------+-----------+ | 1 | Alice | Smith | | 2 | Bob | Jones | +----+------------+-----------+

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 "String Concatenation", we query the relational database engine using declarative SQL. The goal is to concatenate the `first_name` and `last_name` columns with a space in between, aliased as `full_name`. 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 first_name || ' ' || last_name AS full_name 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.

String Concatenation

Easy

Concatenate the first_name and last_name columns with a space in between, aliased as full_name.

Example Scenarios

1Example 1

Input:

users table

id	first_name	last_name
1	Alice	Smith
2	Bob	Jones

Output:

full_name
Alice Smith
Bob Jones

Explanation:

The query retrieves the requested records satisfying all problem requirements.

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