Difference between Strong and Weak Entity
Strong Entity:
A strong entity is not dependent of any other entity in the schema. A strong entity will always have a primary key. are represented by a single rectangle. The relationship of two strong entities is represented by a single diamond.
Various strong entities, when combined together, create a strong entity set.
A weak entity is dependent on a strong entity to ensure the its existence. Unlike a strong entity, a weak entity does not have any primary key. It instead has a partial discriminator key. A weak entity is represented by a double rectangle.
The relation between one strong and one weak entity is represented by a double diamond.
Difference between Strong and Weak Entity:
| S.NO | Strong Entity | Weak Entity |
|---|---|---|
| 1. | Strong entity always has primary key. | While weak entity has partial discriminator key. |
| 2. | Strong entity is not dependent of any other entity. | Weak entity is depend on strong entity. |
| 3. | Strong entity is represented by single rectangle. | Weak entity is represented by double rectangle. |
| 4. | Two strong entity’s relationship is represented by single diamond. | While the relation between one strong and one weak entity is represented by double diamond. |
| 5. | Strong entity have either total participation or not. | While weak entity always has total participation. |
