php - mysql 查询 union 和 mysql_num_rows

Question

SELECT tbl_post_upvote.id AS i ,
       COUNT(user_id) AS c
  FROM tbl_post_upvote 
  LEFT JOIN tbl_post ON (tbl_post.id=tbl_post_upvote.post_id)
 WHERE tbl_post.author_id = 3 and is_seen = 0
 UNION
SELECT tbl_post_downvote.id AS i,
       COUNT(user_id)
 FROM tbl_post_downvote 
 LEFT JOIN tbl_post ON (tbl_post.id=tbl_post_downvote.post_id)
WHERE tbl_post.author_id=3 and is_seen=0

   $r_noti = mysql_query($sq_noti);
   $l = mysql_fetch_assoc($r_noti);
   $l_noti = mysql_num_rows($r_noti);

   if ($l['c'] > 0 && $l['i']!=0) { ?>
      <span class="badge">
          <?= $l_noti; ?>
      </span>
   <?php } ?>

显示结果 我的值为 6 , 0 和c值分别为1、0。 我想删除 0 ,0 行 结果仅为 i 值 6 和 c 值 1

Answer 1

您必须将 GROUP BY i 添加到您的语句中。

请尝试以下操作:

select tbl_post_upvote.id as i ,count(user_id) as c
from tbl_post_upvote left join
     tbl_post 
    on (tbl_post.id=tbl_post_upvote.post_id)
where tbl_post.author_id=3 and is_seen=0
group by i
union
select tbl_post_downvote.id as i,count(user_id)
from tbl_post_downvote left join
     tbl_post
     on (tbl_post.id=tbl_post_downvote.post_id)
where tbl_post.author_id=3 and is_seen=0
group by i