使用最大和分组两次 [英] Using max and group by twice
问题描述
我阅读了有关此主题的一些文章,包括:在两次中使用GROUP BY MySQL ,并且知道这应该与我需要的逻辑相同,但是我只是不知道如何应用它.
I read some articles on this topic including: Use of GROUP BY twice in MySQL and know this should be the same logic I need but I just don’t know how to apply it.
请注意,我知道架构很糟糕(例如,我仍然不明白为什么版本表和发布表是分开的…….)但我无权对其进行更改.
Please note that I know the schema is terrible (I still don’t understand why the edition and published tables are separate for example….) but I don’t have any power to change it.
(我有一些正在使用的敏感信息,所以我将使用一个使用电影的示例来模拟我的问题.)
(I have some sensitive information that I am working with so I will model my problem using an example using movies instead.)
Tables:
Title
TitleID MovieTitle
1 Great Movie #1
2 Great Movie #2
Edition
StockNo editionID EditionText Media TitleID
1 1 Regular Edition DVD 1
2 1 Regular Edition Blue-ray 1
3 2 Extended Version DVD 1
4 2 Extended Version Blue-ray 1
5 1 Regular Edition DVD 2
6 1 Regular Edition Blue-ray 2
7 2 Extended Version DVD 2
8 2 Extended Version Blue-ray 2
Published
StockNo DatePublished
1 1999.01.01
2 2003.01.01
3 2000.01.01
4 1999.01.01
5 1997.01.01
6 1998.01.01
7 2012.01.01
8 2009.01.01
我想返回一行,每一行都是其中一个标题的版本.无论媒体如何,我都想为每个标题版本返回最新的发布日期.
I want to return rows with each row being an edition of one of the titles. For each edition of the title I want to return the latest published date, regardless of the media.
例如:
大动作#1,普通版,最新发布日期
Great move #1, Regular version, Latest_published_date
大电影#1,扩展版本,最新发布日期
Great movie #1, Extended version, Latest_published_date
第2步大动作,普通版,最新发布日期
Great move #2, regular version, Latest_published_date
大电影#2,扩展版本,最新发布日期
Great movie #2, extended version, Latest_published_date
我只是失去了逻辑的海....
I’m just lost in a sea of logic….
WITH Datespublished AS
( Select tt.titleid
,ed.editionID
,pb.datepublished
FROM title tt
left join edition ed on tt.titleid=ed.titleid
left join published pb on pb.stockno=ed.stockno
)
select titleid, editionID, max (datepublished) as maxdate from Datespublished group by titleid THEN editionID?!?!?!?
推荐答案
您可以使用逗号将多个列分组以将它们分组.更改:
You can group by on multiple columns by separating them with a comma. Change:
group by titleid THEN editionID
收件人:
group by titleid, editionID
这篇关于使用最大和分组两次的文章就介绍到这了,希望我们推荐的答案对大家有所帮助,也希望大家多多支持IT屋!