如何通過第一個最大

Question

做一組我有一個查詢，看起來像茨艾倫：

SELECT max(insert_date), 
     creative_id, 
     creative_object 
FROM rtb_creatives 
WHERE adgroup_id = 'agid1608844879' 
     AND is_delete IN (0) 
GROUP BY insert_date, 
      creative_id, 
      creative_object 

例如我有4行： insert_date CREATIVE_ID，creative_object

june 12 a b 
june13 a b 
june 12 c d 
june13 c d 

該查詢返回所有行。

我需要返回

june13 a b 
june13 c d 

如何修改查詢？

Answer 1

剛從GROUP BY條款刪除insert_date：

SELECT max(insert_date) AS insert_date, creative_id, creative_object 
from rtb_creatives 
where adgroup_id='agid1608844879' and is_delete in (0) 
group by creative_id, creative_object 

Answer 2

create table rtb_creatives (insert_date varchar(20), creative_id char(1), creative_object char(1)); 
insert into rtb_creatives (insert_date, creative_id, creative_object) values 
('june 12', 'a', 'b'), 
('june 13', 'a', 'b'), 
('june 12', 'c', 'd'), 
('june 13', 'c', 'd') 
; 

SELECT insert_date, creative_id, creative_object 
from rtb_creatives 
where 
    adgroup_id='agid1608844879' 
    and is_delete in (0) 
    and insert_date = (select max(insert_date) from rtb_creatives) 
group by insert_date, creative_id, creative_object 
; 
+-------------+-------------+-----------------+ 
| insert_date | creative_id | creative_object | 
+-------------+-------------+-----------------+ 
| june 13  | a   | b    | 
| june 13  | c   | d    | 
+-------------+-------------+-----------------+ 

Answer 3

如果你只需要知道，什麼特別creative_id和creative_object最大的日期是，你只需要從GROUP BY條款刪除insert_date ，女巫會導致爲每個組選擇最大日期，我也會改變IN條件以使其更清楚（儘管在這種特殊情況下它並沒有太大區別），如下所示：

SELECT max(insert_date) as insert_date, 
     creative_id, 
     creative_object 
FROM rtb_creatives 
WHERE adgroup_id = 'agid1608844879' 
     AND is_delete = 0 
GROUP BY creative_id, 
      creative_object 

Answer 4

這裏的問題是您的插入日期被定義爲一個字符串。它應該被定義爲日期類型，以便Max（）可以計算正確的順序。假設有另外一個日期，例如8月05日作爲插入日期，那麼Max將返回6月13日。並且請記住，在字符串排序中，在6月13日和6月13日有差異。

當你max（表達式）該表達式不應該在group by子句中。

GROUP BY insert_date, creative_id, creative_object

希望這有助於。