How to fix the Oracle error ORA-30398: illegal JOIN KEY clause?

In this post, you’ll learn more about the Oracle ErrorORA-30398: illegal JOIN KEY clause with the details on why you receive this error and the possible solution to fix it.

Oracle Error Description

ORA-30398: illegal JOIN KEY clause

Reason for the Error ORA-30398: illegal JOIN KEY clause

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.

How to fix the Error ORA-30398: illegal JOIN KEY clause ?

You can fix this error in Oracle by following the below steps

Modify the JOIN KEY clause so that it satisfies the conditions mentioned above.