Gduan,
Glad to hear Oracle is working for you. Good deal.
Relationship lines will only be drawn if your database stores Foreign Key Constraints in it’s schema.
Re: MySQL, I see you are using InnoDB for storage, which does store Foreign Keys. Transaction support is of no consequence to the ER Designer.
You mentioned that you cannot see foreign key information, which is why the ER Designer is not showing the relationship lines.
Are you sure you are creating relationships with dependancy constraints in your schema? Have you observed Foreign keys anywhere at all in the Database Explorer? DB Browser, Table Info View,ER Designer, anywhere?
As Riyad mentioned – update your driver, maybe it isn’t picking them up.
Best,
Brian.