1)

A relational database management system (RDBMS or just RDB) is a common type of database that stores data in tables, so it can be used in relation to other stored datasets.here there will be relation between the rows and columns.

2)

SQL is Structured Query Language. designed for managing data in a relational database management system (RDBMS).It has its own structure and also statemets to fetch the elements.

3)

ER model stands for an Entity-Relationship model.

It is a high-level data model. This model is used to define the data elements and relationship for a specified system.

It develops a conceptual design for the database. It also develops a very simple and easy to design view of data.

In ER modeling, the database structure is portrayed as a diagram called an entity-relationship diagram.

4)

One-to-one relationship

A one-to-one (1:1) relationship means that each record in Table A relates to one, and only one, record in Table B, and each record in Table B relates to one, and only one, record in Table A.

One-to-Many relationship

A one-to-many (1:N) relationship means a record in Table A can relate to zero, one, or many records in Table B. Many records in Table B can relate to one record in Table A. The potential relationship is what's important; for a single record in Table A, there might be no related records in Table B, or there might be only one related record, but there could be many.

Many-to-Many relationship

Many-to-Many relationship in DBMS is a relationship between more than one instance of an entity with more than one instance of another entity i.e. both the entities can have many relationships between each other