Question

大家好，我有以下CTE ...我想要做的是拥有一个Id，然后是状态的连接列表

所以例如...如果我有

1, 1234, Hot
2, 1234, Cold
3, 1234, Warm

我想以

结束

1234,'Hot,Cold,Warm'

我的CTE

with recursive temp_table(RowNumber, Id, Status) as (  
select 
    row_number() over (order by OBJECT_STATUS ) as RowNumber  
    ,OBJECT_ID  
    ,cast(OBJECT_STATUS as varchar(100))  as Status  
from  
    CORE_ORDER_STATUS   
where  
    OBJECT_ID = 'OR000008387722'  
union all  
select   
     a.RowNumber + 1 as NextOne  
     ,b.OBJECT_ID  
    ,a.Status || ',' || cast(b.OBJECT_STATUS as varchar(5))  as Status  
from  
    CORE_ORDER_STATUS b  
inner join  
    temp_table a  
on  
    a.Id = b.OBJECT_ID  
where  
    a.RowNumber = b.NextOne  
)  
select * from temp_table;

Answer 1

您从CTE的SELECT返回每一行。您想要具有最高RowNumber的记录，我认为该记录需要包含HAVING RowNumber=MAX(RowNumber)以及要返回的列的GROUP BY子句。

Answer 2

假设Rob Paller对你的问题的解释是正确的（我认为是这样的），这就是我如何处理这个问题，以及一些针对源数据的kludgy volatile临时表：

create volatile table vt_test as (
select
 '1234' as object_id,
cast ('Hot'  as varchar(1000)) as object_status

) with data
primary index (object_id)
on commit preserve rows;

insert into vt_test values ('1234','Cold');
insert into vt_test values ( '1234','Warm');
insert into vt_test values ( '5678','Red');
insert into vt_test values ( '5678','Blue');
insert into vt_test values ( '5678','Green');


create volatile table vt_two as(
select
row_number() over (partition by object_id order by object_status ) as RN,
object_id,
object_status
from
vt_test) with data
primary index (object_id)
on commit preserve rows;   


with  RECURSIVE CTE (RN,Object_id,Object_Status,counter) as (
SELECT
RN,
object_id,
Object_Status,
cast(1 as integer)
from
vt_two
where RN = 1
UNION ALL
select
b.rn,
b.object_id,
a.object_status || ',' || b.object_status as Object_Status,
counter + 1
from
vt_two a
inner join cte b
on a.object_id = b.object_id
and a.rn = b.counter + 1
) 

select
*
from
CTE
qualify rank() over (partition by object_id order by counter desc) = 1;

哪个会给你：

1   1234    Warm,Hot,Cold   3
1   5678    Red,Green,Blue  3

最后的qualify子句是关键。评论它，它的作用非常清楚。

你必须非常小心递归CTE，至少在Teradata中。编写一个基本上永远不会结束的查询非常容易。

Teradata递归CTE连接行

2 个答案: