How to create ER based on PK and CK

I have Entity A which has a PK(Order #) and candidate key(Order Sequence #), a unique key which i can use to join some Entities.

I have Entity B which has relationship with Entity A as 1 to Many.

if I define Order # as PK in Entity A then i can make the following ER
Entity A(Order #) ---->> Entity B(Order #)

Say now I want to join the Entity A(Order Sequence #) to Entity C. How can do the following join???

Entity A(Order Sequence #) ---->> Entity C(Order Sequence #)

Since already Entity A(Order #) is PK, the Order # column is being added by default by the tool into Entity C as FK…

Let me know if you have any questions…


Hi Srinik,

By “join”, do you mean the join table in sql, or just to connect things in ERD?

If possible, please provide a real case. It would be better than Entity A, B, C.

Best regards,

I meant in ERD only. Will try to send a realtime example soon


Hi Srini,

We look forward to receiving your sample project.

Best regards,