Tables showing up with two: 'one to many' relationships in oracle sql developer

Question

I'm looking through our data and there's a handful of tables in our oracle database that show up with two one to many relationships: https://i.sstatic.net/icGcV.png

I'm not sure why this would be happening, and is it something I should look into getting changed or fixed?

(I did not create this database, I am only trying to understand it!)

Answer 1

Too long for a comment, let's see a very simple example:

CREATE TABLE persons
(
    id      NUMBER PRIMARY KEY,
    name    VARCHAR2(10)
)
/    
CREATE TABLE marriages
(
    wife       NUMBER     REFERENCES persons(id),
    husband    NUMBER     REFERENCES persons(id)
)
/    
CREATE TABLE dogs
(
    id       NUMBER PRIMARY KEY,
    name     VARCHAR2(10),
    owner    NUMBER     REFERENCES persons(id)
)
/

Here you have one table with two different FKs to the same table. At the same time you have another table with a single FK to the same table. So, it's not a problem to fix, but a part of DB design to understand; your DB can be well or bad designed, but the existence of such situations does not say anything about that.