在 Teradata Studio 中使用 PIVOT 时如何连接结果

Question

我有一个表，其中 ID 列的每个值都有一行或多行。现在我想旋转该表并通过 SQL 中的串联来聚合值列的结果值。

下面是我想要使用 R 和 tidyverse 实现的示例。每个人可以与一个或多个其他人建立特定的关系类型：

library(tidyverse)
df <- data.frame(
  person = c("Tina", "Tina", "Tina", "Rachel", "Rachel", "Rachel"),
  relationship_with = c("George", "Jamal", "Thomas", "Joe", "Taylor", "Bruce"),
  relationship_type = c("friend", "friend", "coworker", "friend", "coworker","coworker")
)
df |> pivot_wider(names_from = relationship_type, 
                  values_from = relationship_with,
                  values_fn = ~paste(., collapse=","))


# A tibble: 2 × 3
  person friend       coworker    
  <chr>  <chr>        <chr>       
1 Tina   George,Jamal Thomas      
2 Rachel Joe          Taylor,Bruce

在 Teradata Studio 中使用 SQL 我会尝试以这种方式做同样的事情。

WITH cte AS (
  SELECT person, relationship_with, relationship_type
  FROM df
)
SELECT * 
FROM cte
PIVOT (
  CONCAT(relationship_with) FOR relationship_type IN (
   'friend',
   'coworker'
)
) AS pivot;

不幸的是，上面的代码出现语法错误。似乎必须在 PIVOT 中使用 AVG、MEAN、MAX 等 SQL 聚合函数。 PIVOT 内部不允许使用 CONCAT。我怎样才能使用 SQL 实现我想要的目标？

Answer 1

我找到了一种方法，首先使用

xmlagg()

，然后执行

pivot()

:

-- Preselect your columns here 
with cte as (
 select
 person,
 relationship_with,
 relationship_type
 from df
), 

-- Create another CTE that performs the aggregation using XMLAGG
aggr as (
select 
person, 
relationship_type,
trim( trailing ',' from (
xmlagg(trim(relationship_with) || ',' order by person) 
)) as relationship_with

from  cte 
group by person, relationship_type
)

-- Pivot the aggregated table
-- Using max() here, but this is just because pivot() requires an aggregation function
select
*
from aggr
pivot (max(ZuPartner) FOR Beziehungstyp IN (
  'friend', 'coworker'
)
) pivo;