1)         What is a foreign key?

The foreign key is used to link one or more tables together. It is also known as the referencing key. A foreign key is specified as a key that is related to the primary key of another table. It means a foreign key field in one table refers to the primary key field of the other table. It identifies each row of another table uniquely that maintains the referential integrity. The primary key-foreign key relationship is a very crucial relationship as it maintains the ACID properties of the database sometimes. It also prevents actions that would destroy links between the child and parent tables.

We can define a foreign key into a table as follows:

CONSTRAINT constraint_name]

FOREIGN KEY [foreign_key_name] (col_name, …) REFERENCES parent_tbl_name (col_name,…)

2)          What is a unique key?

A unique key is a single or combination of fields that ensure all values stores in the column will be unique. It means a column cannot stores duplicate values. This key provides uniqueness for the column or set of columns. For example, the email addresses and roll numbers of student’s tables should be unique. It can accept a null value but only one null value per column. It ensures the integrity of the column or group of columns to store different values into a table.

We can define a foreign key into a table as follows:

CREATE TABLE table_name( col1 datatype,

col2 datatype UNIQUE,);

.

3)           What is the difference between a primary key and a unique key?

The primary key and unique key both are essential constraints of the SQL. The main difference among them is that the primary key identifies each record in the table. In contrast, the unique key prevents duplicate entries in a column except for a NULL value. The following comparison chart explains it more clearly:

4)           What is a Database?

A database is an organized collection of data that is structured into tables, rows, columns, and indexes. It helps the user to find the relevant information frequently. It is an electronic system that makes data access, data manipulation, data retrieval, data storing, and data management very easy. Almost every organization uses the database for storing the data due to its easily accessible and high operational ease. The database provides perfect access to data and lets us perform required tasks.

The following are the common features of a database:

• Manages large amounts of data

• Accurate

• Easy to update

• Security
• Data integrity
• Easy to research data

5)           What is meant by DBMS?

DBMS stands for Database Management System. It is a software program that primarily functions as an interface between the database and the end-user. It provides us the power such as managing the data, the database engine, and the database schema to facilitate the organization and manipulation of data using a simple query in almost no time. It is like a File Manager that manages data in a database rather than saving it in file systems. Without the database management system, it would be far more difficult for the user to access the database’s data.

The following are the components of a DBMS:

• Software
  • Data
  • Procedures

• Database Languages
  • Query Processor

• Database Manager
  • Database Engine
  • Reporting

6)           What are the different types of database management systems?

The database management systems can be categorized into several types. Some of the important lists are given below:

• Hierarchical databases (DBMS)
  • Network databases (IDMS)
  • Relational databases (RDBMS

• Object-oriented databases

• Document databases (Document DB)

• Graph databases

• ER model databases

• NoSQL databases

7)           What is RDBMS?

RDBMS stands for Relational Database Management System. It is a database management system based on a relational model. It facilitates you to manipulate the data stored in the tables by using relational operators. RDBMS stores the data into the collection of tables and links those tables using the relational operators easily whenever required. Examples of relational database management systems are Microsoft Access, MySQL, SQL Server, Oracle database, etc.

8)           What is Normalization in a Database?

Normalization is used to minimize redundancy and dependency by organizing fields and table of a database.

There are some rules of database normalization, which is commonly known as Normal From, and they are:

• First normal form(1NF)

• Second normal form(2NF)

• Third normal form(3NF)

• Boyce-Codd normal form(BCNF)

Using these steps, the redundancy, anomalies, inconsistency of the data in the database can be removed.

9)           What is the primary use of Normalization?

Normalization is mainly used to add, delete or modify a field that can be made in a single table. The primary use of Normalization is to remove redundancy and remove the insert, delete and update distractions. Normalization breaks the table into small partitions and then links them using different relationships to avoid the chances of redundancy.

10)              What     are    the    disadvantages    of    not    performing    database Normalization?

The major disadvantages are:

The occurrence of redundant terms in the database causes the waste of space in the disk.

Due to redundant terms, inconsistency may also occur. If any change is made in the data of one table but not made in the same data of another table, then inconsistency will occur. This inconsistency will lead to the maintenance problem and effects the ACID properties as well.