MySQL - Vælg data med en JOIN, men med WHERE-klausuler, der gælder for komplekse og distinkte omkredse

Brug recipient NOT IN (SELECT ...) og author NOT IN (SELECT ...) at udelukke de deltagere, der matcher dine betingelser 1 og 2.

SELECT             
          hia.query_result_id,
          hia.url,
          hia.title,
          hia.article_publication_day,
          hia.media_name,
          hia.author_full_name,
          hia.author_first_name,
          hia.author_last_name,
          hia.author_email,
          ces.sent_at
FROM
          Hobby_ideas_articles hia
LEFT JOIN
          Past_Customer_sent_messages ces
ON
          hia.author = ces.recipient 
            AND ces.recipient NOT IN (
                SELECT recipient
                FROM Past_Customer_sent_messages
                WHERE sent_at > DATE_SUB(NOW(), INTERVAL 3 HOUR)
            )
WHERE
          hia.hobby_id = HOBBY_ID_INPUT_I_HAVE AND         
          hia.author IS NOT NULL
          AND hia.author NOT IN (
            SELECT recipient
            FROM Past_Customer_sent_messages
            WHERE customer_id = CUSTOMER_ID_INPUT_I_HAVE
            AND sent_at > DATE_SUB(NOW(), INTERVAL 30 DAY)
          )

Betingelsen på ces skal være i ON klausul, så du får sent_at = NULL for artikler, der ikke har nogen matchende rækker.