Question

我有两个表类别和照片

分类

CATEGORYID CATEGORY
-------------------
1          Nature
2          Animals
3          Travelling
4          Foods

照片

    PHOTOID   FILENAME    CATEGORYID   URL                                       TIMEUPLOADED
    ------------------------------------------------------------------------------------------------
    1001      file1.jpg   1            http://www.server.com/1001/file1.jpg      2015-12-25 19:21:22
    1002      file2.jpg   1            http://www.server.com/1002/file2.jpg      2015-12-24 19:21:22
    1003      file3.jpg   1            http://www.server.com/1003/file3.jpg      2015-12-22 19:21:22
    1004      file4.jpg   2            http://www.server.com/1004/file4.jpg      2015-12-21 19:21:22
    1005      file5.jpg   2            http://www.server.com/1005/file5.jpg      2015-12-20 19:21:22
    1006      file6.jpg   3            http://www.server.com/1006/file6.jpg      2015-12-19 19:21:22
    1007      file7.jpg   4            http://www.server.com/1007/file7.jpg      2015-12-18 19:21:22
    1008      file8.jpg   3            http://www.server.com/1008/file8.jpg      2015-12-17 19:21:22
    1009      file9.jpg   4            http://www.server.com/1009/file9.jpg      2015-12-16 19:21:22

我希望在相应类别中上传最新照片，其图像数量如下输出

PHOTOID   FILENAME    CATEGORYID  CATEGORY     URL                                       TIMEUPLOADED           IMGCOUNT
----------------------------------------------------------------------------------------------------------------------
1001      file1.jpg   1           Nature       http://www.server.com/1001/file1.jpg      2015-12-25 19:21:22    3
1004      file4.jpg   2           Animals      http://www.server.com/1004/file4.jpg      2015-12-21 19:21:22    2
1006      file6.jpg   3           Travelling   http://www.server.com/1006/file6.jpg      2015-12-19 19:21:22    2
1007      file7.jpg   4           Foods        http://www.server.com/1007/file7.jpg      2015-12-18 19:21:22    2

我尝试使用以下查询

SELECT t1.*,COUNT(*) AS IMGCOUNT FROM photos t1 GROUP BY CATEGORYID order by TIMEUPLOADED desc;

但它没有给出正确的结果

以下查询提供了各自上传的最新照片，但未提供图像计数

 SELECT t1.*,COUNT(*) AS IMGCOUNT FROM photos t1
 LEFT JOIN category t2 on t1.CATEGORYID = t2.CATEGORYID
 JOIN (SELECT CATEGORYID, max(TIMEUPLOADED) maxdt FROM photos GROUP BY CATEGORYID) t3 ON t1.CATEGORYID = t3.CATEGORYID
 AND t1.TIMEUPLOADED = maxdt
 GROUP BY t1.CATEGORYID order by t1.TIMEUPLOADED desc;

Answer 1

我认为这会有效..我创建了一个测试表并运行。您想要为给定类别发布最年轻的照片..以及该类别的总照片数量。

select 

tmp.categoryid,
tmp.mycount,
tmp.maxpid,
p4.filename,
p4.url,
p4.timeuploaded

from 
(select 

p.categoryid, 
count(p.photoid)as mycount,
(select max(photoid) 
  from test.photo p1 
  where p1.categoryid = p.categoryid and p1.timeuploaded = (
                        select max(p2.timeuploaded) from test.photo p2 
                           where p.categoryid = p2.categoryid)) as maxpid

from test.photo p group by p.categoryid)

as tmp

join test.photo p4 on

  p4.photoid = tmp.maxpid

Answer 2

您无法根据需要执行查询，因为CATEGORYID包含多个具有不同PHOTOID的文件名。除非您想从这些类别中获得最小值或最大值：

    select min(`PHOTOID`) as `PHOTOID`, min(`FILENAME`) as `FILENAME`,
     `CATEGORYID`, min(`URL`) as `URL`, min(`TIMEUPLOADED`) as `TIMEUPLOADED`,
     count(*) as 'IMGCOUNT' 
     from photos group by `CATEGORYID` order by `TIMEUPLOADED` desc;

SQLFiddle

如何获取按日期插入的最新记录

2 个答案: