我被困在一个查询在mysql中

Question

我被困在一个查询在mysql中。

我想从表

• 获取最近期的评论的评论应该是最近的评论的博客
• 博客应该是最新的3个博客。只有当他们的状态是启用

记录应该像表的表博客这个
表结构

显示评论&博客

---

 
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') 

为表表结构blog_comment

---

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

及以下查询我写的，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

为此，简单的解决方案将执行2查询您的结果。第一个查询获得博客帖子结果

$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 2

尝试

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％确定）

Answer 3

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 4

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 5

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; 

尝试一个更简单的一个：

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

Answer 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  

个EDITS：

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 

这是使用内部连接将获取最新的博客每个博客

这里3个最新的博客和最新单曲评论。比加入评论和命令他们与日期或ID和限制他们根据您的要求。

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 

的c子查询中找到与每个博客的最新评论的行，使用链接的问题的技术。然后加入blog表以获取适当的博客数据。