Question

我正在编写一个内部有LEFT OUTER JOIN的存储过程。现在我需要将所有具有不同外键总数的行返回到nth（假设为10）！

例如，假设我的表格如下：

    +----+---------------+----------------+--------------+---------------+
    | FK | Name          | UserName       | Asignee      | Comment       |
    +----+---------------+----------------+--------------+---------------+
    | 31 | Test Agent... | Manny Virk     | Sumit Sharda | Test Agent... |
    | 31 | Test Agent... | Manny Virk     | Manny Virk   | Test Agent... |
    | 32 | Test Agent... | Manny Virk     | Gary Pannu   | test          |
    | 32 | Test Agent... | Manny Virk     | Sunny Tiwana | test          |
    | 32 | Test Agent... | Manny Virk     | Manny Virk   | test          |
    | 33 | Test Agent... | Rachel Stalony | Gary Pannu   | test          |
    | 33 | Test Agent... | Rachel Stalony | Sunny Tiwana | test          |
    | 33 | Test Agent... | Rachel Stalony | Manny Virk   | test          |
    | 34 | Test Agent... | Manny Virk     | Gary Pannu   | test          |
    | 34 | Test Agent... | Manny Virk     | Sunny Tiwana | test          |
    | 34 | Test Agent... | Manny Virk     | Manny Virk   | test          |
    | 35 | Test TeamW... | Manny Virk     | Sunny Tiwana | adsf asdf ... |
    | 35 | Test TeamW... | Manny Virk     | Manny Virk   | adsf asdf ... |
    | 36 | New Agent ... | Manny Virk     | Sumit Sharda | Test comme... |
    | 36 | New Agent ... | Manny Virk     | Sunny Tiwana | Test comme... |
    | 36 | New Agent ... | Manny Virk     | Manny Virk   | Test comme... |
    | 37 | Test TeamW... | Manny Virk     | Sunny Tiwana | Some comme... |
    | 37 | Test TeamW... | Manny Virk     | Manny Virk   | Some comme... |
    | 38 | qwer qwer.... | Manny Virk     | Sunny Tiwana | some new c... |
    | 38 | qwer qwer.... | Manny Virk     | Manny Virk   | some new c... |
    | 42 | asdfsafdsa... | Manny Virk     | Gary Pannu   | NULL          |
    | 42 | asdfsafdsa... | Manny Virk     | Manny Virk   | NULL          |
    | 43 | 20161214 J... | Manny Virk     | Gary Pannu   | My Test co... |
    | 43 | 20161214 J... | Manny Virk     | Sunny Tiwana | My Test co... |
    | 41 | Happy Wedd... | Manny Virk     | Gary Pannu   | Svi togeth... |
    | 41 | Happy Wedd... | Manny Virk     | Manny Virk   | Svi togeth... |
    | 44 | Call all l... | Manny Virk     | Sumit Sharda | Call all l... |
    | 44 | Call all l... | Manny Virk     | Manny Virk   | Call all l... |
    | 45 | Reperition... | Manny Virk     | Gary Pannu   | NULL          |
    | 45 | Reperition... | Manny Virk     | Manny Virk   | NULL          |
    | 46 | Some Task     | Manny Virk     | Sumit Sharda | Some Task ... |
    | 46 | Some Task     | Manny Virk     | Manny Virk   | Some Task ... |
    | 47 | asdf          | Manny Virk     | Sumit Sharda | 6twdfwu       |
    | 47 | asdf          | Manny Virk     | Manny Virk   | 6twdfwu       |
    | 48 | Test Daily... | Manny Virk     | Sumit Sharda | Test Daily... |
    | 48 | Test Daily... | Manny Virk     | Manny Virk   | Test Daily... |
    | 49 | Test Weekl... | Manny Virk     | Sumit Sharda | Test Weekl....|
    +----+---------------+----------------+--------------+---------------+

我希望程序能够将所有行返回到FK = 43，包括所有FK = 43，因为这是最后的第10个不同的FK！

有人可以帮我写这个SQL吗？

Answer 1

在标准SQL中执行此操作的一种方法是：

select t.*
from t
where t.fk in (select t2.fk
               from t t2
               group by t2.fk
               order by t2.fk
               fetch first 10 rows only
              );

确切的语法可能因数据库而异，尤其是fetch first子句。

Answer 2

select
 FK,Name,UserName,Asignee,Comment      
from
(

select
 FK,Name,UserName,Asignee,Comment      
 ,dense_rank() over (order by FK) dr
 from table
 ) a
 where dr<=10

SQL - 获取第n个不同外键

2 个答案: