An entity-relationship (ER) diagram is a graphical representation of the data and relationships in a database system. It can help to design, document and communicate the logical structure of a database. In this blog post, we will show how to create an ER diagram for a multi-vendor e-commerce app, which allows multiple sellers to offer their products or services on a common platform.
The main entities in our ER diagram are:
- User: A person who can register, login, browse, buy and review products or services on the app. A user can also be a seller, who can create, update and delete their own products or services.
- Product: An item or service that a seller offers on the app. A product has attributes such as name, description, price, category, image, etc.
- Order: A transaction between a buyer and a seller for one or more products. An order has attributes such as date, status, total amount, shipping address, etc.
- OrderItem: A sub-entity that represents a single product in an order. It has attributes such as quantity, unit price, etc.
- Review: A feedback that a buyer gives to a seller for a product or service. It has attributes such as rating, comment, date, etc.
The main relationships in our ER diagram are:
- A user can have zero or more orders. An order must belong to one and only one user. This is a one-to-many relationship between User and Order.
- A user can have zero or more reviews. A review must belong to one and only one user. This is a one-to-many relationship between User and Review.
- A user can have zero or more products. A product must belong to one and only one user. This is a one-to-many relationship between User and Product.
- An order can have one or more order items. An order item must belong to one and only one order. This is a one-to-many relationship between Order and OrderItem.
- A product can have zero or more order items. An order item must belong to one and only one product. This is a one-to-many relationship between Product and OrderItem.
- A product can have zero or more reviews. A review must belong to one and only one product. This is a one-to-many relationship between Product and Review.
The following image shows the ER diagram for our multi-vendor e-commerce app:
