Database

Connectivity means how many instances of one entity are associated with how many instances of another entity. The connectivity of a relationship can be classified into 4 types:
These are:
1.) One to one (1 : 1)
2.) One to many (1 : M)
3.) Many to one (M : 1)
4.) Many to many (M : N)
So, this answer is correct.

There are seven types of keys in relational database. These are:
1.) Primary key
2.) Candidate key
3.) Super key
4.) Foreign key
5.) Alternate key
6.) Artificial key
7.) Composite key
So, this is the correct answer.

This is the correct answer. The entity set that doesn’t have sufficient attributes to form a primary key and relies on another for its identification is called a weak entity set. It doesn’t have a primary key. So, this is the correct answer.

This is the correct answer.  

This is the correct answer. There are five types of attribute in database. These are:
1.) Simple attribute
2.) Composite attribute
3.) Single-valued attribute
4.) Multivalued attribute
5.) Derived attribute
There is no attribute named unary. Unary is a type of relation which is known as degree of relation (unary, binary, ternary, etc.).
So, this is the correct answer according to the question.

Statement Q is correct because primary key and foreign key can exist in the same relation. Moreover, foreign key can refer to the primary key in the same relation. So, this is correct.

There are five types of attributes in relational database. These are:
1.) Simple attribute
2.) Composite attribute
3.) Single-valued attribute
4.) Multivalued attribute
5.) Derived attribute
So, this is the correct answer.

This is the correct choice. Statement R is true because we can apply restrictions on the values of attributes; these are known as constraints. So, this answer is correct.

There are 3 types of data models present in DBMS. These are:
1.) Object based data model
2.) Record based data model
3.) Physical data model
So, this is the correct answer.

This is the correct answer.  

Statement P is correct because a candidate key is a key that uniquely identifies a row in a relation. So, this cannot be null as it uniquely identifies a row. Statement R is correct because primary key is chosen from a set of candidate keys. In other words, all the candidate keys are the candidates for the primary key. So, in this way. all the candidate keys are primary keys. So, this is the correct answer. Statement Q is false because if the primary key is composed of more than one attribute, then these attributes are known as prime attributes, not super attributes.

All of the given options are true. So, this is the correct choice.

Connectivity can also be used to describe a relation. Connectivity means how many instances of one entity are associated with how many instances of another entity. It can be:

1. One to one (1 : 1)
2. One to many (1 : M)
3. Many to one (M : 1)
4. Many to many (M : N)
   So, this answer is correct.

This is the correct choice.

There are 3 types of record-based data models. These are:
1.) Hierarchical model
2.) Network model
3.) Relational model
So, this is the correct choice.