Database Schema – Everything You Need To Know

A database schema is a blueprint or a visual representation of a database. It defines a set of guidelines that control a database. It shows how data is organized and how the components are associated in a database. The design of a database schema can impact how efficiently the database runs and how fast one can retrieve information. While creating a database, a developer should know how its different aspects work together. In this blog, you will learn what is a database schema and its different types.

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Let us begin by understanding what is a database schema.

Database Schema Overview

Database Schema Definition: A database schema is the outline of the architecture or logical view of a database. It is a collection of metadata that represents entities and the relationship among them. Database schemas are a vital component of database management systems (DBMS).

A database schema describes:

• Organization of data
• Relationships between tables in a database

Database designers develop schemas to help administrators, developers, and programmers understand how a database is structured and interact with the database easily. To create an efficient database schema, the designers need to know what components are necessary and how they will connect.

What Does a Database Schema Include?

A database schema provides a way for logically grouping and showing database objects such as:

• Tables
• Fields
• Functions
• Relationships
• Packages

A database schema object includes the following:

• All relevant data, no important data is omitted
• Consistent formatting of the data entries
• Unique keys for each entry
• Tables with multiple columns
• Each column in a table has a name and data type

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Database Schema Types

There are three types of database schemas: physical schema, logical schema, and view schema.

1. Physical Schema

This schema represents the actual storage of data and its form of storage such as files, indices in secondary storage. It is the actual code that is used to create the structure of a database. For example, in MySQL, you will use SQL to create a database with tables.

2. Logical Schema

This schema explains how data is organized in tables. It defines all the logical constraints that need to be applied to the data stored. It describes tables, views, and integrity constraints. Different schemas use different syntax to represent the logical architecture and constraints.

3. View Schema

It is the view-level design of a database. It defines the end-user interaction with the database systems.

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Creating Database Schemas

Below are the statements for creating schema in different database systems:

MySQL

We use the “CREATE SCHEMA” statement in MySQL to create a database. In MySQL, the CREATE SCHEMA and CREATE DATABASE statements are similar.

SQL Server

We use the “CREATE SCHEMA” statement to create a schema in the SQL server.

Oracle Database

The “CREATE USER” statement creates a schema in the Oracle database. It is because, in Oracle Database, a schema is already created with each database user. CREATE SCHEMA statement enables users to populate their schema with tables and views and allows access to those objects without requiring multiple SQL statements for multiple transactions.

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Types of Database Schemas Design

The six most popular types of schemas are:

Flat Model

It is a 2-D array with each column containing the same type of data. The elements within a row are related to each other. It is suitable for small and simple applications that do not require complex data.

Hierarchical Model

It has a tree-like structure with a root node that links to its child nodes. Each child node and the parent node have a one-to-many relationship. The hierarchical model is suitable for nested data. It is presented by XML or JSON files.

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Network Model

The network model schema is similar to the hierarchical design. The difference between the two is that a network model allows a many-to-many relationship, unlike a hierarchical model that allows a one-to-many relationship. It mostly helps in mapping and spatial data. It is ideal for representing workflows.

Relational Model

This model is used for the relational databases that store data as relations of the table. It is ideal for Object-Oriented Programming applications.

Star Schema

The star schema works on “Facts” and “Dimensions” wherein the fact refers to the numerical data point that runs business processes. Dimensions are a description of fact. It allows users to structure the data of RDBMS. The star schema helps in analyzing large datasets.

Snowflake Schema

It is an adaptation of the star schema. The difference between the two is that in the star schema, the “Fact” table contains the main data points and references to its dimension tables. On the other hand, in a snowflake schema, the dimension tables can have their own dimension tables. This schema helps analyze huge data.

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Conclusion

In this blog, we learned about different types of database schemas. We also discussed the different schema designs and how to create a schema. This information will help you visualize how to structure a database by giving you a high-level view of the structure and relationship of the tables in your database.