What is RDBMS?

A Relational Database Management System (RDBMS) incorporates the relational data model in which one database entry is referenced to another database entry. The Structured Query Language (SQL) is used to perform operations on RDBMS.

In this management system, the data is stored in the form of tables, rows, and columns. The tables have interdependencies that are created through keys called foreign keys.

Below are a few ways that tables are linked:

• One-to-one relation: One table record may be linked to one record in another table.
• One-to-many relation: One table record may be linked to more than one record in another table.
• Many-to-many relation: Many table records may be linked to many records in another table.
• Many-to-one relation: Many table records may be linked to one record in another table.

Below are a few important features of RDBMS:

• It uses rows and columns to store data in a structured format.
• It allows data to be normalized.
• It supports ACID properties.
• It can be distributed to support higher throughput.

Let’s learn some important database concepts that are common in most of the databases.

Primary key

A primary key is a column used to uniquely identify each row from a table. For example, the row number is the primary key in an excel sheet as it can be used to select a row uniquely.

Foreign key

A foreign key is a column that references the primary key of another table. It is used to link two tables. For example, a house belongs to an owner. The table of houses will store a reference to the owner. That reference is a foreign key.

Normalization

Normalization is an important concept that improves database structure, maintains data integrity, and reduces data redundancy. It can be used while designing a relational database, but it can also be used for a NoSQL database.

There are some forms of normalization which are applied in order. These forms are 1NF, 2NF, 3NF, 4NF, and BCNF.

ACID properties

A relational database supports transactions that obey ACID properties. These properties are:

• Atomicity ensures that the entire transaction either takes place at once or does not happen at all.

• Consistency ensures that the database stays consistent before and after a transaction.

• Isolation ensures that multiple transactions never create inconsistency of database state.

• Durability ensures that once the transaction is completed, the changes persist to the database even if a system failure occurs.

Some examples of RDBMS databases are MySQL, Oracle, IBM, PostgreSQL, Microsoft SQL Server.

MongoDB supports transactions starting from version 4.0.