Filtering Records Using EXISTS Subqueries

SELECT
    p.post_id,
    p.title,
    p.created_at
FROM
    posts p
WHERE EXISTS (
    SELECT 1
    FROM comments c
    WHERE c.post_id = p.post_id
    AND c.status = 'approved'
);

How it works: This query retrieves posts that have at least one approved comment. The `EXISTS` operator is used to check for the presence of any row returned by the subquery. It's often more efficient than a `JOIN` when you only need to verify existence rather than retrieve data from the joined table. The subquery returns '1' if an approved comment for the current post exists, and `EXISTS` evaluates to true, including the post in the result set.