Question

我想添加一个where子句以确保video_count大于零。只应返回在video_category.video_id中引用一次或多次的类别。

因为video_count不是任何表格中的字段，所以我无法做到这一点。

这是查询。

SELECT category . * , (
        SELECT COUNT( * )
        FROM video_category
        WHERE video_category.category_id = category.category_id
        ) AS 'video_count'
        FROM category
        WHERE category.status = 1
    AND video_count > '0'
        AND publish_date < NOW()
        ORDER BY updated DESC;

感谢您的帮助。

Answer 1

SELECT c.title,COUNT(vc.category_id) 
  FROM categories c
     , video_categories vc 
 WHERE c.id=vc.category_id 
   AND c.status=1 
   AND c.publish_date < NOW() 
 GROUP BY c.id;

Answer 2

我认为你可以使用GROUP BY来实现它; HAVING条款。

SELECT category . *
     , COUNT(v.*)  as video_count
  FROM category c
     , video_category v
 WHERE v.category_id = c.category_id
   AND c.status = 1
   AND publish_date < NOW()
 GROUP BY v.category_id 
HAVING COUNT(v.*) > 0
ORDER BY updated DESC;

不检查

Answer 3

这是理想的做法：

SELECT c.id, COUNT(vc.id)
  FROM category as c
  LEFT JOIN video_category as vc
  on c.categoryid = vc.categoryid
 WHERE c.status = 1
   AND vc.categoryid is not null
   AND c.publish_date < NOW()
 GROUP BY c.id;

另外，请确保您真的需要选择c。*

选择*可能会影响性能。

Answer 4

使用子查询重写：

SELECT *
FROM (
    SELECT category . * , (
        SELECT COUNT( * )
        FROM video_category
        WHERE video_category.category_id = category.category_id
        ) AS 'video_count'
        FROM category
        WHERE category.status = 1
        AND publish_date < NOW()
    ) dummy
WHERE video_count > '0'
    ORDER BY updated DESC;

Answer 5

我不知道这是否是最好的答案，但它对我有用。

SELECT category. * , (

SELECT COUNT( * )
FROM video_category
WHERE video_category.category_id = category.category_id
) AS 'video_count'
FROM category
WHERE category.status =1
AND (

SELECT COUNT( * )
FROM video_category
WHERE video_category.category_id = category.category_id
) >0
AND publish_date < NOW( )
ORDER BY updated DESC

Answer 6

select category.*, count(video_category.category_id) as c
from category inner join video_category using(category_id)
where category.status = 1
and publish_date < now()
group by video_category.category_id
having c > 0
order by updated desc

这应该可以解决问题

不能在相关列上使用where子句

6 个答案: