ORA-30398: illegal JOIN KEY clause
Cause: 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.
Action: Modify the JOIN KEY clause so that it satisfies the conditions mentioned above.
ORA-30398: illegal JOIN KEY clause 这是一个Oracle数据库的SQL错误，指在SQL语句中，JOIN KEY子句出现了非法的关键字。
1. 检查JOIN KEY子句的语法是否正确；
2. 检查是否在JOIN KEY子句中使用了Oracle数据库的保留字，如果使用了，则可以在关键字前加上双引号，从而获得正确的解析结果；
3. 检查JOIN KEY子句语句中若有表列表进行关联，则必须检查关联的表列是否有效。