35. What is RDBMS? Explain its features

RDBMS stands for Relational Database Management System. It organizes data into related rows and columns.
Features
It stores data in tables.
Tables have rows and column.
These tables are created using SQL.
And data from these tables are also retrieved using SQL.

36. What is an Entity-Relationship diagram?

It is a graphical representation of tables with the relationship between them.

37. Define referential integrity?

It is the rules that are applied when the relationships are created. It ensures integrity of data and prevents inconsitent data into the tables.

38.Define Primary key and Foreign key

A column or combination of columns that identify a row of data in a table is Primary Key.
A key in a table that identifies records in other table in called a foriegn key.

39. Define alternate key

There can be a key apart from primary key in a table that can also be a key. This key may or may not be a unique key. For example, in an employee table, empno is a primary key, empname is a alternate key that may not be unique but still helps in identifying a row of the table.

40. What is the normalization?

Normalization is the way of organizing data in a database by removing redundancy and inconsistent dependency.
Database normalization has the rules to be followed while creating databases.
Each rule is called as normal form.
First Normal form states - Remove duplicate column and identify each set of related data with a primary key.
Second normal form - Create relationship between master and master detail tables using foreign key.
Third normal form - Remove the fields that do not depend on the primary key.

41.Define Index

Index is the way to order the records in a database according to the field values. It is the way to have fast access to the particular information. Indexes are created to the columns that are queried frequently.