Designing a complete database schema for an online merchandise store is a complex task and would require a detailed understanding of the store’s specific requirements. However, I can provide a simplified example schema to give you an idea:

1. Users Table:

• UserID (Primary Key)
• Username
• Password
• Email
• First Name
• Last Name
• Address
• Phone Number

1. Products Table:

• ProductID (Primary Key)
• Name
• Description
• Price
• Stock Quantity

1. Categories Table:

• CategoryID (Primary Key)
• Category Name

1. ProductCategories Table (Many-to-Many Relationship):

• ProductCategoryID (Primary Key)
• ProductID (Foreign Key)
• CategoryID (Foreign Key)

1. Orders Table:

• OrderID (Primary Key)
• UserID (Foreign Key)
• Order Date
• Status (e.g., Pending, Shipped, Delivered)

1. OrderItems Table (Many-to-One Relationship with Orders):

• OrderItemID (Primary Key)
• OrderID (Foreign Key)
• ProductID (Foreign Key)
• Quantity
• Subtotal

1. Payment Table:

• PaymentID (Primary Key)
• OrderID (Foreign Key)
• Payment Date
• Payment Amount
• Payment Method

1. Reviews Table:

• ReviewID (Primary Key)
• ProductID (Foreign Key)
• UserID (Foreign Key)
• Rating
• Comment
• Review Date

This is a basic structure to get you started. Depending on the complexity of your store, you may need to expand and optimize the schema further. Additionally, you’ll need to consider aspects like security, indexing, and data validation in a real-world implementation.