Chapter 4, Problem 4.1RQ

Define each of the following terms:

1. determinant
2. functional dependency
3. transitive dependency
4. recursive foreign key
5. normalization
6. composite key
7. candidate key
8. normal form
9. partial functional dependency
10. enterprise key
11. surrogate primary key

Program Plan Intro

(a)

Definition of determinant

Explanation of Solution

Determinant is an attribute of the database table that is used todetermines the corresponding values of another column in the same table uniquely. As given in the definition any primary key attribute, candidate key attribute, or any non-prime attribute, non-candidate attribute can be a determinant. Consider the table given below:

Employee_ID	Employee_name	Employee_salary
101	ram	20000
102	Shyam	10000
103	Rita	30000

In the given table the employee_ID is considered as a determinant and it is also a prime key attribute here. as here, only employee_ID can identify the value of the other columns uniquely, whereas no other can.

Program Plan Intro

(b)

Definition of functional dependency

Explanation of Solution

It helps in identifying the table attributes which are related and dependent to each other. For example: if there are two columns in the table A and B. Then the functional dependency between them is represented as:

A→B

Here, all the attribute in the column A is functionally dependent on B. Consider the table given below:

Employee_ID	Employee_name
101	ram
102	Shyam
103	Rita

Here employee_ID→employee_name

(As if we know the employee ID, then we definitely get the name of the employee), i.e., employee_ID is functionally dependent on employee_name

Program Plan Intro

(c)

Definition of transitive dependency

Explanation of Solution

A dependency is to be transitive only if it is formed by two functional dependencies indirectly. Consider the relations given below:

A→B

B→C

Here, A is functionally dependent on B, and B is functionally dependent on C. As here, C is formed by the combination of two functional dependencies; hence, we can conclude that C is having transitive dependency. It only occurs when there are three or more attribute in a given relation. It helps us in normalizing the database in 3NF (i.e., 3 rd Normal Form)

Program Plan Intro

(d)

Definition of recursive foreign key

Explanation of Solution

Foreign key is a key which represents the primary key attributes in the table. Recursive foreign key is a foreign key which refers to the primary key in the same table. Consider a scenario of table having details of employee and managers. Here, managers are also employees. In the column of employee ID the ID of all the employees are present. In the column of the manager ID, only some employees that are managers have their unique identity, and the rest is null. Here employee ID is not null, but the manger ID can be null, in the case of those employees which are not managers.

Program Plan Intro

(e)

Definition of normalization

Explanation of Solution

Normalization is used to remove the redundancy (i.e., duplication and replication) and dependency of the data.it helps in making searching, sorting, indexing, retrieval of data, etc. easy. It also helps in increasing efficiency, accessibility of data. Type of normalization is given below:

1. 1 NF
2. 2 NF
3. 3 NF
4. Boycee Codd Normal Form
5. 6 NF

Program Plan Intro

(f)

Definition of composite key

Explanation of Solution

It is a combination of two or more columns in the table. It can be used to identify each row in the table uniquely. Here, when the candidate key is combined it must be unique; however, if it is taken individually then this it is not necessary to be unique. It is also known as concatenated key. Consider an example of student ID and class ID, here it is also possible that a student is enrolled in 2 or more subject. And a course ID is also associated with the more than one student ID. In case to identify the proper details of student with course ID, we need to use both values of course ID and the student ID i.e., candidate key.

Program Plan Intro

(g)

Definition of candidate key

Explanation of Solution

An attribute or a combination of attribute that helps in identifying a row in relation.it value is not null and unique for attributes.it can be simple or composite key. There can be multiple candidate keys in the database, and it is also possibly that among that candidate key one is the primary key.

Program Plan Intro

(h)

Definition of normal form

Explanation of Solution

Normal forms are given below:

1. 1NF(First normal form )
2. Second normal form
3. Third normal form
4. BCNF
5. Fourth normal form

• 1 NF: table must follow the given properties for being in the first normal form:

1. Attributes should be single valued.

2. Columns name must be unique

3. Here, ordering of data does not matter

• Second normal form: table must follow the given properties for being in the second normal form:

  1. It should be in 1 NF

  2. There is no partial dependency

• Third normal form: table must follow the given properties for being in the third normal form

1. it should be in 2 NF

2. There is no transitive dependency

• BCNF (Boyce Codd Normal Form): it is a upgraded version of the 3 NF.

1. Here, the given should be in 3 rd normal form

2. And for each functional dependency (X(Y) there should be a super key. >

• Fourth normal form: conditions are given below:

1. It sould be in BCNF

2. And, there is no multivalued attribute.

Program Plan Intro

(i)

Definition of partial functional dependency

Explanation of Solution

Partial functional dependency means that a non-prime attribute is functionally dependent on a part of a candidate key.

Program Plan Intro

(j)

Definition of enterprise key

Explanation of Solution

The term enterprise key is given by expert developer to the prime key if it is unique for the whole database, and not only for a relation. And the concept of making the prime key more like as in the object-oriented environment is known as an object identifier.

Program Plan Intro

(k)

Definition of surrogate primary key

Explanation of Solution

Surrogate primary key is developed to make the key structure easy. This key is developed for the purpose of data analysis. This key is not displayed to users. Surrogate primary key can be available when:

1. There is a composite primary key.
2. The natural primary key is inefficient.
3. The natural primary key is recycled as there it needs to be unique every time.