Vælg flere feltduplikater fra MySQL-databasen

En meget hacket løsning er at få thread_id sorteret efter view_count i en GROUP_CONCAT . Derefter kan vi bruge strengoperationer til at få thread_id med minimum view_count .

I din SELECT klausul i stedet for t.thread_id , kan du prøve følgende:

SUBSTRING_INDEX(GROUP_CONCAT(DISTINCT t.thread_id 
                             ORDER BY t.view_count ASC 
                             SEPARATOR ','), 
                ',', 
                1) AS thread_id_with_minimum_views

Nu, baseret på SELECT forespørgsel for at identificere duplikerede poster med Minimum visning, DELETE forespørgsel om at slette sådanne poster fra xf_thread tabel vil være som følger:

DELETE t_delete FROM xf_thread AS t_delete 
INNER JOIN (SELECT CAST(SUBSTRING_INDEX(GROUP_CONCAT(DISTINCT t.thread_id ORDER BY t.view_count ASC SEPARATOR ','), ',', 1) AS UNSIGNED) AS tid_min_view 
            FROM (SELECT * FROM xf_thread) t 
            INNER JOIN xf_post p ON p.thread_id = t.thread_id 
            WHERE t.first_post_id = p.post_id 
              AND t.user_id = 0 
              AND t.reply_count < 2 
            GROUP BY t.title, t.username, p.message 
            HAVING Count(t.title) > 1 
               AND Count(t.username) > 1 
               AND Count(p.message) > 1 
            ORDER BY t.thread_id) AS t_dup 
  ON t_delete.thread_id = t_dup.tid_min_view