Who is the weak entity set represented in the ER model?

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.

What is a weak entity in database?

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 the relation between author and book?

What is the relationship between books and authors? An author can write several books and a book can have more than one author, so this is an example of a many-to-many relationship. A many-to-many relationship can only be represented by creating a new table in the database.

What are the different types of attributes in ER model?

There are 5 different types of attributes in DBMS.

• Simple Attributes. Simple Attributes are independent attributes that cannot be classified further.
• Composite Attribute.
• Single Valued Attributes.
• Multi-Valued Attributes.
• Derived Attributes.
• Key Attributes.

What do you mean by cardinality What are different kinds of Cardinalities?

In other words, cardinality describes a fundamental relationship between two entities or objects. There are three relationship types or cardinalities: one-to-one, one-to-many, and many-to-many. Entity-Relationship (ER) diagrams are used to describe the cardinality in databases.

What is a strong entity in ER diagram?

Strong Entity is independent to any other entity in the schema. A strong entity always have a primary key. 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 are maximum Cardinalities?

Maximum Cardinality. Sets the maximum number of items that the user can select from a relationship. If you set the minimum cardinality to greater than 0, you must set the maximum cardinality to a number at least as large If you do not enter a maximum cardinality, the default is 999.

Which one is incorrect related to ER diagram?

Many ER diagram mistakes fit into one of these four categories: Incorrect relationships between entities. Using an entity instance instead of an entity. Confusing an attribute with an entity.