What is the entity of employee?

What is the entity of employee?

Next, the Employee entity is the child of the Person entity that then defines the Employee entity. Each of these entities has different attributes that are inherited by the children under them, as well as their identity.

Can an entity have a relationship with itself?

It is possible for an entity to have a relationship with itself; for example, an entity Staff could have a relationship with itself, as one member of staff could supervise other staff. This is known as a recursive or involute relationship, and would be represented in an entity-relationship diagram as shown below.

Can an entity have no attributes?

Since it is not possible to have an entity without any attributes, an occurrence of an entity without attributes clearly indicates that the attributes are specified elsewhere.

Can a weak entity have a relationship that is not weak with the identifying entity?

1 Answer. Yes, weak entity sets can participate in non-identifying relationships with other entities.

How do you represent a weak entity?

Weak entity is represented by double rectangle. The relation between one strong and one weak entity is represented by double diamond. Weak entities are represented with double rectangular box in the ER Diagram and the identifying relationships are represented with double diamond.

How do you identify relationships and entities?

Identifying Entity Relationships in DBMS

  1. Weak Entity. Weak Entity is dependent on Strong Entity and does not have a primary key.
  2. Strong Entity. Other entities are dependent on Strong Entity and it has a key attribute i.e. a primary key and represented as a single rectangle.
  3. Identifying Relationships.

How many relationships can an entity have?

This is how a relationship between two tables is established. There are three types of relationships that can exist between two entities.

How many attributes can an entity have?

In some instances, an entity will have more than one attribute that can serve as a primary key. Any key or minimum set of keys that could be a primary key is called a candidate key. Once candidate keys are identified, choose one, and only one, primary key for each entity.

Do all entities have to have attributes?

You can not define entities without properties/attributes, even if they have primary key. Entity types in partitioning relationships (represented by the triangle symbol) exist without primary key in a Conceptual Model. But they exist only if they possess attributes equally.

What is an entity that does not require a relationship to another entity for identification?

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. The foreign key is typically a primary key of an entity it is related to.

How do you convert a weak entity to a strong entity?

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 weak entity relationship?

Can a person be an employee of an employer?

Only a person can be an “employee.”. An entity can contract with an employer to provide services. Those working for the contracted entity and providing the actual services would be employees or contractors of the contracted entity. But it is not possible for an entity itself to be an employee. I hope that you find this information helpful.

How is an entity related to another entity?

Here EmployeeId is the primary key for the Employee table and the same key is present on the primary key and foreign key of the EmployeeDetail table. Through an association, an entity can be related to the other entities in the entity framework.

Can a entity have a 1 : m relationship?

Create an additional entity and relate it to the original entity with a 1:M relationship. (*) 11. An entity can have repeated values and still be in 1st Normal Form. True or False?

How to move an attribute to a new entity?

Move the attribute STORE LOCATION to a new entity, STORE, with a UID of STORE ID, and create a relationship to the original entity. (*) Move the attribute STORE LOCATION to a new entity, STORE, with a UID of STORE LOCATION, and create a relationship to the original entity. 15. Any Non-UID attribute must be dependent upon the entire UID.

Only a person can be an “employee.”. An entity can contract with an employer to provide services. Those working for the contracted entity and providing the actual services would be employees or contractors of the contracted entity. But it is not possible for an entity itself to be an employee. I hope that you find this information helpful.

Do you have to be a member of Staff for both entities?

Optional for one entity, mandatory for the other: A member of staff does not have to be placed in a department, but all departments must have at least one member of staff. Optional for both entities: A member of staff might be assigned to work in a department, but this is not compulsory.

Create an additional entity and relate it to the original entity with a 1:M relationship. (*) 11. An entity can have repeated values and still be in 1st Normal Form. True or False?

What are the attributes of a particular entity?

A particular entity will have a value for each of its attributes. The attribute values that describe each entity become a major part of the data stored in the database. Figure 7.3 shows two entities and the values of their attributes.