Question

我想使用JOIN将行转换为oracle 10g中的列。我不想使用DECODE或XMLAGG函数。我的表格结构如下：

GROUP_ID    ENTITYID    GROUP_ENTITYID
1           A997        A995
2           A997        A993
3           A997        A990
4           A988        A987
5           A988        A982
6           A988        A980
7           A979        A975
8           A979        A974
9           A979        A973

我希望以下列格式获取数据：

ENTITYID    GROUP_ENTITYID

A979    A979,A975,A974,A973
A988    A988,A987,A982,A980
A997    A997,A995,A993,A990

你们能告诉我怎么做吗？

提前致谢。

Answer 1

Tim Hall拥有各种string aggregation techniques available in Oracle的规范列表。

使用联接来组合数据既不实际也不高效。如果您碰巧知道EntityID将映射到其他三个Group_EntityID值，则可以使用联接

SELECT a.entity_id, 
       a.entity_id || ','  ||
         a.group_entityID || ',' ||
         b.group_entityID || ',' ||
         c.group_entityID
  FROM table_name a,
       table_name b,
       table_name c
 WHERE a.entityID = b.entityID
   AND a.entityID = c.entityID
   AND a.group_entityID > b.group_entityID
   AND b.group_entityID > c.group_entityID

但如果与特定Group_EntityID相关联的EntityID值的数量发生变化，那么该方法既不特别有效，也不具有特别的灵活性。

我通常更喜欢创建用户定义的聚合函数（Tim列表中的一个选项）并执行类似

的操作

SELECT entityID, entityID || ',' || string_agg( group_entity_id )
  FROM table_name
 GROUP BY entityID;

如果您想在不创建任何其他对象或功能的情况下执行此操作，可以在Tim的网站上使用SYS_CONNECT_BY_PATH方法

SQL> ed
Wrote file afiedt.buf

  1  with x as (
  2    select 1 group_id, 'A997' entityID, 'A995' group_entityID from dual union all
  3    select 2, 'A997', 'A993' from dual union all
  4    select 3, 'A997', 'A990' from dual union all
  5    select 4, 'A998', 'A987' from dual union all
  6    select 5, 'A998', 'A982' from dual union all
  7    select 6, 'A998', 'A980' from dual union all
  8    select 7, 'A979', 'A975' from dual union all
  9    select 8, 'A979', 'A974' from dual union all
 10    select 9, 'A979', 'A973' from dual
 11  )
 12  select entityID,
 13         entityID || ',' ||
 14           ltrim( max( sys_connect_by_path( group_entityID, ','))
 15                     keep(dense_rank last order by group_id),
 16                  ',') group_entityID
 17    from (select group_id,
 18                 entityID,
 19                 group_entityID,
 20                 row_number() over (partition by entityID
 21                                        order by group_id) curr,
 22                 row_number() over (partition by entityID
 23                                        order by group_id) - 1 prev
 24            from x)
 25   group by entityID
 26  connect by prev = PRIOR curr
 27      and entityID = PRIOR entityID
 28*  start with curr = 1
SQL> /

ENTI GROUP_ENTITYID
---- ------------------------------
A979 A979,A975,A974,A973
A997 A997,A995,A993,A990
A998 A998,A987,A982,A980

在oracle 10g中将行转换为列

1 个答案: