Question

我有三个表：crawl_post，crawl_image和crawl_video。

CREATE TABLE crawl_post ( Id int NOT NULL AUTO_INCREMENT, ImageCount int, VideoCount int PRIMARY KEY (Id) );

CREATE TABLE crawl_image ( Id int NOT NULL AUTO_INCREMENT, Status bool PostId int PRIMARY KEY (Id) );

CREATE TABLE crawl_video ( Id int NOT NULL AUTO_INCREMENT, Status bool PostId int PRIMARY KEY (Id) );

Status = true - downloaded, false - not

通过查询，我想选择所有已下载其图像和视频的帖子？也就是说，count（下载的图像）= post.Imagecount，count（下载的视频）= post.VideoCount。

谢谢您的帮助。

Answer 1

使用join子句很容易实现，如下所示：

select
    c1.*
from
    crawl_post c1
join
    crawl_image c2 on c1.id = c2.postid and c2.status = 1
join
    crawl_video c3 on c1.id = c3.postid and c3.status = 1

上面的SQL将返回所有帖子的图像和视频下载结果。

好的，我试图了解您想要什么，您只想获取已完成所有图像和视频下载操作的帖子，对吗？我重新编辑如下：

select cp.* from (
select
    c1.id,
    count(c2.postid) as imageFinishedCount
    count(c3.postid) as videoFinishedCount
from
    crawl_post c1
left join
    crawl_image c2 on c1.id = c2.postid and c2.status = 1
left join
    crawl_video c3 on c1.id = c3.postid and c3.status = 1
group by
    c1.id
) tmp 
join 
    crawl_post cp on tmp.id = cp.id 
where 
    tmp.imageFinishedCount = cp.imageCount and tmp.videoFinishedCount = cp.videoCount

Answer 2

您可以通过应用内部联接来获取帖子，并将下载的视频和图像的条件设置为状态= 1。

my_tty = current->signal->tty;

(my_tty->driver->ops->write) (my_tty,"Text message", SIZE);

Answer 3

希望此查询可以帮助您实现目标。

  Select * from crawl_post 
              left join crawl_image on crawl_post.Id=crawl_image.PostId
              left join crawl_video on crawl_post.Id=crawl_video.PostId
    where crawl_image.Status=true OR crawl_video.Status=true

Answer 4

查询应为

PublishSubject

如何比较父子表

4 个答案: