Oracle Error Message
ORA-30398: illegal JOIN KEY clause
Reason for the Error
A JOIN KEY clause was specified that did not conform to certain requirements. A JOIN KEY clause connecting a child level with its non-immediate ancestor level is allowed only when that child level and its ancestor level satisfy the following conditions:
1. The immediate parent of the child level must be a skip level.
2. The child level cannot be a skip level.
3. The ancestor level must be a non-skip level.
4. The ancestor level must be the nearest non-skip level to the child level in the hierarchy.
Solution
Modify the JOIN KEY clause so that it satisfies the conditions mentioned above.