Question

为什么下面的查询在oracle中不起作用？

select * from ENTITY_OWNERSHIP EO
where 
(select count (*) 
    from (
      select USER_ID 
      from ENTITY_OWNERSHIP 
      where ENTITY_OWNERSHIP.ENTITY_ID = EO.ENTITY_ID
    )
) > 0

它产生“ORA-00904：”EO“。”ENTITY_ID“：无效的标识符”。但是当我用精确值替换EO.ENTITY_ID时，例如10181，那么它就可以了。

更新：完整查询如下所示：

select * from ENTITY_OWNERSHIP EO
where 
(select count (*) 
    from (
      select USER_ID 
      from ENTITY_OWNERSHIP 
      where ENTITY_OWNERSHIP.ENTITY_ID = EO.ENTITY_ID

      intersect

      select distinct group_id
      from USERS.GROUPS 
      start with GROUP_ID in (select GROUP_ID from USERS.LK_GROUPS where USER_ID=10001)
      connect by prior PARENTGROUP_ID=GROUP_ID 
    )
) > 0

Answer 1

如果按照基础知识进行操作， CORRELATED Subquery可以访问相关表格。但是当有 INNER subquery时， INNER Query将首先尝试执行...因此，条件中的另一个表格无法被占用，因为它们在那个时间点不可用。理解这一点的捷径是......正如其他答案所述......

SELECT A.* FROM TABLE A
WHERE EXISTS
 (SELECT 'X' FROM TABLE B WHERE B.ID = A.ID)

现在，相关子查询可以访问A.

select * from ENTITY_OWNERSHIP EO
where 
EXISTS
(
      select USER_ID 
      from ENTITY_OWNERSHIP 
      where ENTITY_OWNERSHIP.ENTITY_ID = EO.ENTITY_ID

      intersect

      select distinct group_id
      from USERS.GROUPS 
      start with GROUP_ID in (select GROUP_ID 
                               from USERS.LK_GROUPS
                             where USER_ID=10001)
      connect by prior PARENTGROUP_ID=GROUP_ID
)

Answer 2

我认为您可以使用exists来代替：

select *
from ENTITY_OWNERSHIP EO
where exists (
      select USER_ID 
      from ENTITY_OWNERSHIP 
      where ENTITY_OWNERSHIP.ENTITY_ID = EO.ENTITY_ID

      intersect

      select distinct group_id
      from USERS.GROUPS 
      start with GROUP_ID in (select GROUP_ID from USERS.LK_GROUPS where USER_ID=10001)
      connect by prior PARENTGROUP_ID=GROUP_ID 
    );

ORA-00904：子查询中的标识符无效

2 个答案: