mysql distinct statement not working

Question

$query = "SELECT DISTINCT t.task_id, e.url,e.error_id, p.page_rank, e.scan_status, e.url_is_route,e.url_is_route,e.forbidden_word,e.google_host_fail,e.google_cache_fail,e.google_title_fail,e.robots_noindex_nofollow,e.xrobots_noindex_nofollow,e.title_fetch_warn,e.h1_fail,e.h2_fail,e.h3_fail,e.h1_warn,e.h2_warn,e.h3_warn 
       FROM `error_report` AS e 
       INNER JOIN task_pages AS t ON t.task_id=e.task_id 
       INNER JOIN `pages` AS p ON p.page_id=t.page_id 
       WHERE t.task_id=" . $this->task_id ; 

我希望查詢只能通過t.task_id區分。問題是，當我添加更多的字段時，查詢不再有區別。是否還有一種方法僅通過t.task_id選擇不同的？的

Answer 1

代替distinct使用group by

$query = "SELECT t.task_id, e.url,e.error_id, p.page_rank, e.scan_status, e.url_is_route,e.url_is_route,e.forbidden_word,e.google_host_fail,e.google_cache_fail,e.google_title_fail,e.robots_noindex_nofollow,e.xrobots_noindex_nofollow,e.title_fetch_warn,e.h1_fail,e.h2_fail,e.h3_fail,e.h1_warn,e.h2_warn,e.h3_warn 
      FROM `error_report` AS e 
      INNER JOIN task_pages AS t ON t.task_id=e.task_id 
      INNER JOIN `pages` AS p ON p.page_id=t.page_id 
      WHERE t.task_id=" . $this->task_id 
      ."group by t.task_id"; 

Answer 2

如果你添加更多的字段，你應該使用IIRC GROUP BY。

請注意，您的額外字段應爲爲集合，例如， MIN，MAX等.MySQL更爲寬容，並且顯示了每個領域的第一個價值（雖然不是很明顯）。