In ERD, can a weak entity have more than one relationship with its supporting entity?
If a weak entity can have more than one relationship with its supporting entity, can all of them be identifying relationships, or only one of them can be the identifying relationship?
The weak entity can not be uniquely identified without reference to another entity. This means that a foreign key to another entity is part of its primary key.
As a consequence, a weak entity cannot have more than one identifying relationship with another entity. If it would, it's identity would no longer be unique.
However nothing prevents it from having ANOTHER, different , relationship to the same supporting entity. Let's take an example: a PROJECT is a strong entity. a TASK is a weak entity whose identity depends on the PROJECT. But a task could have a secondary relationship to PROJECT, not related to the task's identity, for example to express that a that a task is one project is to refer to a project.