Summary: In this tutorial, you’ll learn how to design a PostgreSQL database for your application.
Business Requirements
We’ll design a database for a simple inventory management system.
Let’s start with the business requirements:
“Our inventory management system empowers warehouse users to efficiently manage inventory from multiple warehouses.
It streamlines product management, enabling users to handle products across tags, categories, and brands effectively.
Additionally, the system records all goods receipt/issue transactions, ensuring smooth and efficient inventory management.”
Important Questions
To design a database for the inventory management system, you need to ask the following important questions:
- What tables should the database have?
- What are the relationships between these tables?
Identifying Tables
The inventory system allows multiple users to access and perform inventory management tasks, so the database should have a table called users.
Each user may have a profile to store additional information like first name, last name, and phone. Therefore, the database should have a table called profiles.
The system needs to manage multiple warehouses. To track these warehouses, we can create a warehouses table.
The inventory system manages multiple products across tags, brands, and categories, so the database should have four more tables: tags, brands, categories, and products.
When warehouse users receive or issue products, they record the transactions. The database should have a transactions table to record these transactions.
To provide a more granular view of product quantities across warehouses, we can create a table called inventories.
Table Relationships
Let’s find the relationship between tables.
One-to-One Relationships
Each user has a profile, and a profile is linked to a user. The relationship between the user and profile is one-to-one.
In PostgreSQL, each row in the users table has a corresponding row in the profiles table.
One-to-Many Relationships
Each brand has many products, and a product belongs to a brand. The relationship between brand and product is one-to-many.
Similarly, each category has many products, and each product belongs to a category. The relationship between category and product is one-to-many.
In PostgreSQL, one row in the categories table is associated with multiple rows in the products table. Likewise, one row in the brands table is related to multiple rows in the products table.
A user may record zero or more transactions, and a transaction is recorded by one and only one user. So, the relationship between the user and the transaction is one-to-many.
A warehouse may have multiple transactions, and a transaction belongs to one and only one warehouse. The relationship between the warehouse and the transaction is one-to-many.
A product may have multiple transactions, and a transaction belongs to one product. The relationship between product and transaction is one-to-many.
A category can have subcategories. The relationship between category and subcategories is one-to-many. We can use the same categories table to store both categories and subcategories.
Many-to-Many Relationships
A product has one or more tags, and one tag has many products. The relationship between product and tag is many-to-many.
In PostgreSQL, we can model the many-to-many relationship by using two one-to-many relationships by creating a link table called product_tags.
