SQL查詢來獲取

Question

組

的最大日我想從每個WishContent基礎上，wishContent.wishId最新的日期，這樣，如果我有wishContents這樣的：

ID DATE 
#1 : 09-03-2016 
#1 : 08-03-2016 
#1 : 03-04-2016 
#2 : 09-02-2016 
#2 : 04-01-2016 

然後我只想：

#1 09-03-2016 
#2 09-02-2016 

SELECT 
     wish.Status, 
     wish.Id, 
     wish.User, 
     wish.CompletionDate, 
     wishContent.Content, 
     wishContent.Title, 
     wishContent.Country, 
     wishContent.City, 
     wishContent.IsAccepted, 
     wishContent.moderator_Username, 
     MAX(wishContent.Date) AS max_date 
     FROM `wish` JOIN wishContent on wish.Id = wishContent.wish_Id 
     GROUP BY wish.Id where wish.Date 
     ORDER BY max_date DESC 

任何人都可以幫助我嗎？

Answer 1

我想你需要一個額外的連接來獲得所需的結果：

SELECT 
     w.Status, 
     w.Id, 
     w.User, 
     w.CompletionDate, 
     wc.Content, 
     wc.Title, 
     wc.Country, 
     wc.City, 
     wc.IsAccepted, 
     wc.moderator_Username, 
     wcMax.max_date 
     FROM wish AS w 
     JOIN (SELECT wish_Id, MAX(wishContent.Date) AS max_date 
      FROM wishContent 
      GROUP BY wish_Id 
    ) AS wcMax ON w.Id = wcMax.wish_Id 
     JOIN wishContent AS wc on wcMax.wish_Id = wc.wish_Id AND wc.Date = wcMax.max_date 
     WHERE wish.Date 
     ORDER BY max_date DESC 

Answer 2

嘗試這個

SELECT * FROM (
SELECT 
     wish.Status, 
     wish.Id, 
     wish.User, 
     wish.CompletionDate, 
     wishContent.Content, 
     wishContent.Title, 
     wishContent.Country, 
     wishContent.City, 
     wishContent.IsAccepted, 
     wishContent.moderator_Username, 
     MAX(STR_TO_DATE(wishContent.Date,'%d-%m-%Y')) AS max_date 
     FROM `wish` JOIN wishContent on wish.Id = wishContent.wish_Id 
     GROUP BY wish.Id 
    ) AS t 
     ORDER BY t.max_date DESC; 

我假設你的日期格式爲DD-MM-YYYY。