Question

什么是热门标签的查询？的 Tabels

blog_tags
id  name
1   tag1
2   tag2
3   tag3
4   tag4
5   tag5




blog_post_tags
id  post_id     blog_tag_id
1   1       2
2   2       2
3   1       3
4   3       5
5   4       2



output
tag2
tag3
tag5

我开始写这样的查询：

SELECT bt.id, bt.name, bpt.blog_tag_id
FROM
blog_tags bt
RIGHT JOIN
blog_post_tags bpt
ON
bt.id = bpt.blog_tag_id
ORDER BY bt.name ASC

它给出了blog_post_tags中使用的标签的输出，但我希望标签根据受欢迎程度进行排序。

Answer 1

SELECT  blog_tags.name, t.used_cnt FROM blog_tags
INNER JOIN (
    SELECT blog_tag_id, count(*)  as used_cnt
    from blog_post_tags
    group by blog_tag_id 
)t 
ON blog_tags.id = t.blog_tag_id
ORDER BY t.used_cnt DESC

Answer 2

只需将right join替换为inner join，将group by代码ID替换为：

select bt.name
from blog_post_tags bpt
join blog_tags bt on bpt.blog_tag_id = bt.id
group by bt.id, bt.name -- Edit: fixing for some strict dbs
order by count(bpt.post_id) desc

请参阅sqlfiddle中的demo。

Answer 3

我认为这样的查询应该有效：

select name from (select blog_tag_id,count(*) as cnt from blog_post_tags group by blog_tag_id order by cnt dsc ) as a inner join blog_tags on a.blog_tag_id = blog_tags.id

什么将在博客实施中查询热门标签？

3 个答案: