使用重复值更新Oracle SQL表

Question

我希望有人可以提供帮助。我需要从包含重复项的select更新表。

ID;CLASS;VALUE;NEW
1;a;a3;
1;b;s6;
1;c;b99;
2;a;s3;
2;b;r6;
2;c;b99;
3;a;s5;
4;a;r6;
4;b;a3;

查看我的示例表，有一个colum NEW ，我必须更新。在示例中，手动填充 NEW 列。

这是目标（如表col NEW所示）：

1.通过ID查找重复项（HAVING COUNT（*）＆gt; 1或类似内容）

1. UPDATE TABLE SET NEW = CLASS || '_'||值 WHERE CLASS ='a'或'b'

很容易吗？

提前谢谢

Answer 1

背后的逻辑并不完全清楚;这可能是一种方式。

设置：

create table yourTable(id, class, value, new) as
(
    select 1, 'a', 'a3', cast (null as varchar2(10)) from dual union all
    select 1, 'b', 's6', null from dual union all
    select 1, 'c', 'b99', null from dual union all
    select 2, 'a', 's3', null from dual union all
    select 2, 'b', 'r6', null from dual union all
    select 2, 'c', 'b99', null from dual union all
    select 3, 'a', 's5', null from dual union all
    select 4, 'a', 'r6', null from dual union all
    select 4, 'b', 'a3', null from dual
)  

查询：

merge into yourTable t1
using (
        select listagg(value, '_') within group (order by class) as new,
               id      
        from yourTable
        where class in ('a', 'b')
        group by id
        having count(distinct class) = 2
      ) t2
on (    t1.id = t2.id
    and t1.class in ('a', 'b')
   )
when matched then
update set t1.new = t2.new

结果：

SQL> select *
  2  from yourTable;

        ID C VAL NEW
---------- - --- ----------
         1 a a3  a3_s6
         1 b s6  a3_s6
         1 c b99
         2 a s3  s3_r6
         2 b r6  s3_r6
         2 c b99
         3 a s5
         4 a r6  r6_a3
         4 b a3  r6_a3

9 rows selected.