SQL
Fetch Related Data with LEFT JOIN
Learn how to combine rows from two or more tables based on a related column, retrieving all records from one table and matching records from another.
SELECT p.id, p.title, p.content, u.username AS author_username
FROM posts p
LEFT JOIN users u ON p.author_id = u.id
WHERE p.published = TRUE;
How it works: This query uses a LEFT JOIN to retrieve all posts and their corresponding author usernames. If a post does not have a matching author in the 'users' table (e.g., author_id is NULL or references a non-existent user), the user-related columns will show NULL. This ensures all posts are returned, regardless of author presence, which is crucial for displaying content even if author data is missing.