排序由最大值

Question

我有一个表，看起来像这样在Oracle DB：

TransactionID  Customer_id  Sequence  Activity 
----------   -------------  ----------  ----------- 
1     85    1    Forms 
2     51    2    Factory 
3     51    1    Forms 
4     51    3    Listing 
5     321    1    Forms 
6     321    2    Forms 
7     28    1    Text 
8     74    1    Escalate 

而且我希望能够理清所有行sequence最高为每customer_id。 我有一个MAX()函数我可以使用的顺序，但基于customer_id莫名其妙？

我想查询的结果是这样的：

TransactionID  Customer_id  Sequence  Activity 
----------   -------------  ----------  ----------- 
1     85    1    Forms 
4     51    3    Listing 
6     321    2    Forms 
7     28    1    Text 
8     74    1    Escalate 

Answer 1

select t1.* 
from your_table t1 
inner join 
(
    select customer_id, max(Sequence) mseq 
    from your_table 
    group by customer_id 

) t2 on t1.customer_id = t2.customer_id and t1.sequence = t2.mseq 

Answer 2

SQL Fiddle

的Oracle 11g R2架构设置：

CREATE TABLE tbl (TransactionID, Customer_id, Sequence, Activity) AS 
      SELECT 1, 85, 1, 'Forms' FROM DUAL 
UNION ALL SELECT 2, 51, 2, 'Factory' FROM DUAL 
UNION ALL SELECT 3, 51, 1, 'Forms' FROM DUAL 
UNION ALL SELECT 4, 51, 3, 'Listing' FROM DUAL 
UNION ALL SELECT 5, 321, 1, 'Forms' FROM DUAL 
UNION ALL SELECT 6, 321, 2, 'Forms' FROM DUAL 
UNION ALL SELECT 7, 28, 1, 'Text' FROM DUAL 
UNION ALL SELECT 8, 74, 1, 'Escalate' FROM DUAL; 

查询1：

SELECT 
    MAX(TransactionID) KEEP (DENSE_RANK LAST ORDER BY Sequence) AS TransactionID, 
    Customer_ID, 
    MAX(Sequence) KEEP (DENSE_RANK LAST ORDER BY Sequence) AS Sequence, 
    MAX(Activity) KEEP (DENSE_RANK LAST ORDER BY Sequence) AS Activity 
FROM tbl 
GROUP BY Customer_ID 
ORDER BY TransactionID 

Results：

| TRANSACTIONID | CUSTOMER_ID | SEQUENCE | ACTIVITY | 
|---------------|-------------|----------|----------| 
|    1 |   85 |  1 | Forms | 
|    4 |   51 |  3 | Listing | 
|    6 |   321 |  2 | Forms | 
|    7 |   28 |  1 |  Text | 
|    8 |   74 |  1 | Escalate | 

Answer 3

请试试吧

with cte as 
(
    select Customer_id,MAX(Sequence) as p from Tablename group by Customer_id 
) 
select b.* from cte a join Tablename b on a.p = b.Sequence where a.p = b.Sequence and a.Customer_id=b.Customer_id order by b.TransactionID