Question

我已经制作了一个视图（加入四个表格），如下所示：

ID  |  BookID  |    date    |  points  |
 1  |    11    | 2014-11-01 |    15    |
 1  |    11    | 2015-01-01 |    16    |
 1  |    11    | 2014-12-01 |    17    |
 1  |    12    | 2014-02-11 |    18    |
 1  |    12    | 2014-03-11 |    19    |
 1  |    12    | 2014-04-11 |    15    |
 1  |    13    | 2014-12-23 |    121   |
 1  |    14    | 2014-01-15 |    113   |
 1  |    14    | 2014-02-08 |    112   |

我希望此视图的结果如下

ID  |  BookID  |    Date     |  points  |
 1  |    11    |  2015-01-01 |    16    |
 1  |    12    |  2014-04-11 |    15    |
 1  |    13    |  2014-12-23 |    121   |
 1  |    14    |  2014-02-08 |    112   |

它应该像Distincit Book ID一样具有最大日期并显示为分隔点。到目前为止，我已经通过加入和分组与日期一起尝试了该组。但它有点过了，因为我无法找到解决方案。

我的查询是：

SELECT m1.* FROM viewPoints m1 LEFT JOIN viewPoints m2 
ON (m1.BookID = m2.BookID AND m1.Date < m2.Date)
WHERE m1.ID= 1 and m2.Date IS NULL

ORDER BY m1.BookID

任何帮助！在此先感谢。

Answer 1

也许这就是你想要的？

select v.* 
from viewPoints v
join (
    select 
       BookID, 
       max(date) max_date 
    from viewPoints
    where points is not null 
    group by BookID
) v2 on v.BookID = v2.BookID and v.date = v2.max_date
where v.points is not null
order by v.BookID

Sample SQL Fiddle

示例输出：

| ID | BOOKID |                            DATE | POINTS |
|----|--------|---------------------------------|--------|
|  1 |     11 |  January, 01 2015 00:00:00+0000 |     16 |
|  1 |     12 |    April, 11 2014 00:00:00+0000 |     15 |
|  1 |     13 | December, 23 2014 00:00:00+0000 |    121 |
|  1 |     14 | February, 08 2014 00:00:00+0000 |    112 |

Answer 2

CREATE VIEW [BOOKLIST] AS
SELECT m1.* FROM viewPoints m1 LEFT JOIN viewPoints m2 
ON (m1.BookID = m2.BookID AND m1.Date < m2.Date)
WHERE m1.ID= 1 and m2.Date IS NULL
ORDER BY m1.BookID    

SELECT ID, DISTINCT BookID, Date, points FROM BOOKLIST
WHERE Date BETWEEN "start date" AND "end date"

Answer 3

SELECT * 
 FROM tablename
  WHERE DATE
 IN (

   SELECT MAX( DATE ) 
   FROM tablename
   GROUP BY bookid
   ORDER BY DATE DESC
  )
 ORDER BY DATE DESC

获取不同和最新记录的mysql查询

3 个答案: