如何在Oracle的单行中返回重复ID的冗余行

Question

我有一个审计类的表，我们根据其他表中的一些触发器存储一些信息。

ID，Changed_Column，OldValue，NewValue将可用。现在有可能使用相同的Id，会有3-4个重复，因为更改后的列将有不同的值，我希望将它们合并为单行，并为exmaple获取数据，

ID   ChangedColumn OldValue NewValue
1    Name           Bob     Roy
1    Age            26      28  
1    Section        B       C

当我们选择现在，它将显示所有行为分隔，但我想要自我连接和检索只有一个记录通过合并基于ID值

预期的结果是，

ID   Name               Age           Section     ChangedColumns
1    was :Bob now : Roy was:26 now:28 Was:B now:C Name, Age, Section

Answer 1

要对列名进行分组，可以使用listagg函数。若要将行转换为列，请使用Pivot函数。

with tab as(
  select 1 as id,    'Name' as col,    'Bob' as OldValue ,     'Roy' as NewValue from dual union all
  select 1 as id,    'Age',            '26',      '28' as NewValue from dual union all  
  select 1 as id,    'Section',        'B',       'C' as NewValue from dual 
)
select * 

from (
select id
      ,t.col as col
      ,max('was: '|| t.OldValue || ' now: ' || t.NewValue) as val
      ,listagg(t.col,',') within group(order by t.id) OVER (PARTITION BY null)  as ChangedColumn 
from tab t
group by id,t.col

) 
pivot ( max(val)  for col in('Name','Age','Section'));

db<>fiddle https://dbfiddle.uk/?rdbms=oracle_18&fiddle=de694207bf1221e95372b7953bffe1a3

Answer 2

使用条件聚合似乎非常简单：

select id,
       max(case when col = 'Name' then str end) as name,
       max(case when col = 'Age' then str end) as age,
       max(case when col = 'Section' then str end) as section
from (select t.*, ('was: ' || OldValue || ' now: ' || NewValue) as str
      from t
     ) t
group by id;

这里是db<>fiddle。