How do you represent a strong and weak entity in ER Diagram?
Strong entity is represented by a single rectangle. Weak entity is represented by a double rectangle. 4. Two strong entity’s relationship is represented by a single diamond.
What is weak entity and strong entity?
The Key Difference between Strong and Weak Entity is that a Strong Entity has a primary key whereas a Weak Entity does not have a primary key. Weak entity is dependent on a strong entity whereas a Strong entity is independent not dependent on any other.
What is weak entity in ER Diagram?
A weak entity is a type of entity which doesn’t have its key attribute. It can be identified uniquely by considering the primary key of another entity. For that, weak entity sets need to have participation. In above ER Diagram examples, “Trans No” is a discriminator within a group of transactions in an ATM.
What is strong entity and weak entity explain with example?
Example of Strong and Weak Entity The example of a strong and weak entity can be understood by the below figure. The Strong Entity is Professor, whereas Dependent is a Weak Entity. ID is the primary key (represented with a line) and the Name in Dependent entity is called Partial Key (represented with a dotted line).
What is a strong entity in ER diagram?
Strong Entity is independent to any other entity in the schema. In ER diagram, a strong entity is represented by rectangle. Relationship between two strong entities is represented by a diamond. A set of strong entities is known as strong entity set.
How can I make my weak entity strong?
Though weak entity set can be converted into strong entity set by simply adding appropriate attributes, this approach results in the redundant storage of primary key. ii. The primary key of a weak entity set can be inferred from its relationship with the strong entity set.
What is a strong entity?
Definition of Strong Entity The Strong Entity is the one whose existence does not depend on the existence of any other entity in a schema. It is denoted by a single rectangle. A strong entity always has the primary key in the set of attributes that describes the strong entity.
What are the strong entity in ER diagram?
In ER diagram, a strong entity is represented by rectangle. Relationship between two strong entities is represented by a diamond. A set of strong entities is known as strong entity set.
What is strong entity example?
For example: a ROOM can only exist in a BUILDING. On the other hand, a TIRE might be considered as a strong entity because it also can exist without being attached to a CAR.
What makes a weak entity?
In a relational database, a weak entity is an entity that cannot be uniquely identified by its attributes alone; therefore, it must use a foreign key in conjunction with its attributes to create a primary key.
What is weak entity set explain with example?
A weak entity set is an entity set that does not contain sufficient attributes to uniquely identify its entities. In other words, a primary key does not exist for a weak entity set. However, it contains a partial key called as a discriminator. Discriminator can identify a group of entities from the entity set.
What is weak entity example?
A weak entity is one that can only exist when owned by another one. For example: a ROOM can only exist in a BUILDING. On the other hand, a TIRE might be considered as a strong entity because it also can exist without being attached to a CAR.
What is a weak entity set?
A weak entity set is one that can’t be identified by its own attributes. Weak entity sets are identified, at least partially, by their relationship with another entity set. This means that a weak entity set’s primary key will contain a foreign key.
What is a weak entity relationship?
A weak entity is an entity that must defined by a foreign key relationship with another entity as it cannot be uniquely identified by its own attributes alone. Actions, which are represented by diamond shapes, show how two entities share information in the database. In some cases, entities can be self-linked.
What is a weak relationship?
A weak relationship, also known as a non-identifying relationship, exists if the primary key of the related entity does not contain a primary key component of the parent entity. By default, relationships are established by having the primary key of the parent entity appear as a foreign key (FK) on the related entity (also known as the child entity).