Distinguish between a Weak (or non-identifying) and a Strong (or identifying) relationshipbetween entities.

In the context of Entity-Relationship (ER) models in database design, the difference between weak (non-identifying) and strong (identifying) relationships between entities can be explained as follows:

1. Strong (Identifying) Relationship:

   • A strong or identifying relationship is when the primary key of the related entity contains the primary key of the "parent".
   • In other words, the existence of the related entity depends on the "parent" entity. If the "parent" entity is deleted, the related entity will also be deleted. This is also known as a parent-child relationship.
   • For example, in a database of orders and products, each order line (child) must be associated with a specific order (parent). If the order is deleted, the order line would also be deleted.

2. Weak (Non-Identifying) Relationship:

   • A weak or non-identifying relationship is when the primary key of the related entity does not contain the primary key of the "parent".
   • In this case, the related entity does not depend on the "parent" entity. If the "parent" entity is deleted, the related entity will not be deleted.
   • For example, in a database of products and suppliers, each product (child) may be associated with a supplier (parent). However, if a supplier is deleted, the product would not necessarily be deleted.

In summary, the key difference between weak and strong relationships is the dependency of the child entity on the parent entity. In a strong relationship, the child entity cannot exist without the parent, while in a weak relationship, the child entity can exist independently of the parent.