我被困在mysql中的一个查询中

Question

我被困在mysql中的一个查询中。

我想从表中获取最新评论

• 评论应该是博客上的最新评论
• 博客应该是最新的3个博客。
• 显示评论＆amp;仅当博客状态为已启用时才显示博客

记录应该是这样的 表格博客

的表格结构

---

  
blog_id int - primary (auto increment)
blog_title       -varchar
blog_desc        -varchar
blog_image       -varchar
blog_tags        -varchar
tot_comments     -int
blog_creater     -varchar
blog_create_date -datetime
blog_status      -enum ('Enable','Disable')

表 blog_comment

的表格结构

---

comment_id       -int (auto increment)  
fk_blog_id       -int  
comment          -varchar  
comment_by       -varchar  
email            -varchar  
comment_date     -datetime  
comment_status   -enum ('Enable','Disable')

下面是我写的查询，但我得到的结果是错误的。

SELECT b.blog_title,b.blog_image, bc.*
FROM blog_comments  bc, blog b
WHERE bc.comment_status='Enable'
AND b.blog_status='Enable'
AND b.blog_id=bc.fk_blog_id
GROUP BY bc.fk_blog_id    
ORDER BY bc.comment_date DESC 
LIMIT 0,3

输出

---

Answer 1

SELECT b.blog_title,b.blog_image, bc.*
FROM blog b
left join (
Select * from 
blog_comments bc
WHERE bc.comment_status='Enable'
GROUP BY bc.fk_blog_id    
having max(bc.comment_date) =  bc.comment_date
) bcc on b.blog_id=bcc.fk_blog_id
where
b.blog_status='Enable'
ORDER BY b.blog_create_date desc
LIMIT 0,3

试试这个

Answer 2

试试这个：

SELECT * FROM blog_comments  bc, blog b
WHERE `bc.comment_status`='Enable'
AND `b.blog_status`='Enable'
AND `b.blog_id`=bc.fk_blog_id
ORDER BY `bc.comment_date` DESC LIMIT 1;

尝试更简单的一个：

SELECT * FROM `blog_comment` WHERE 'blog_status'='Enable' AND 'blog_id'='$blogidherefromtitle' ORDER BY 'comment_date' DESC LIMIT1

Answer 3

为此，简单的解决方案将执行2查询您的结果。第一个查询获取博客帖子结果

$db_blog="select blog_id,blog_title from blog where blog_ststus='Enable'";
$que=mysql_query($db_blog); 
while($row=mysql_fetch_object($que))
{
    echo $row->blog_title;
    $db_comment="select comment from blog_comments where fk_blog_id=".$row->blog_id." and comment_status='Enable' order by comment_date desc";
    $quec=mysql_query($db_comment);
    while($comment=mysql_fetch_object($quec))
    {
         echo $comment->comment;
    }
}

Answer 4

试

SELECT b.blog_title,b.blog_image, bc.*
FROM blog_comments AS bc, blog AS b
WHERE bc.comment_status='Enable'
AND b.blog_status='Enable'
AND b.blog_id=bc.fk_blog_id
GROUP BY bc.fk_blog_id    
ORDER BY bc.comment_date DESC 
LIMIT 0,3;

（我不是100％肯定）

Answer 5

SELECT b.blog_title,b.blog_image, bc.*
FROM blog_comments  bc JOIN blog b ON bc.fk_blog_id = b.blog_id
WHERE bc.comment_status='Enable'
AND b.blog_status='Enable'
GROUP BY bc.fk_blog_id    
ORDER BY bc.comment_date DESC 
LIMIT 0,3

Answer 6

尝试此查询

SELECT 
  bc.* 
FROM
  blog AS b 
  INNER JOIN (SELECT id , MAX(id) AS MaxID FROM blog) AS bl ON bl.id = b.id 
  LEFT JOIN blog_comment AS bc ON bc.fk_blog_id = b.id 
ORDER BY bc.comment_id DESC 
LIMIT 3     

编辑：

SELECT 
  bc.* 
FROM
  blog AS b 
  INNER JOIN (SELECT id , MAX(id) AS MaxID FROM blog GROUP BY id) AS bl ON bl.id = b.id 
  INNER JOIN (SELECT MAX(id) , fk_blog_id FROM blog_comment  GROUP BY id) AS bc ON bc.fk_blog_id = b.id 
ORDER BY bc.comment_id DESC 
LIMIT 3

这是针对每个博客的3个最新博客和最新单个评论

此处使用内部联接将获取最新的博客。而不是加入评论并按日期或身份对其进行排序，并根据您的要求对其进行限制。

Answer 7

select b.blog_title, b.blog_image, bc.*
from blog b join
(select bc.*
 from bc join (select fk_blog_id, max(comment_date) latest_date
               from blog_comment
               where comment_status = 'Enable'
               group by fk_blog_id) latest
 on bc.fk_blog_id = latest.fk_blog_id and bc.comment_date = latest_date) c
on b.blog_id = c.fk_blog_id
where b.blog_status = 'Enable'
order by c.comment_date desc
limit 0, 3

c子查询使用链接问题中的技术查找每个博客的最新评论行。然后将其与blog表联接以获取相应的博客数据。