DBT Modeling Example
Source Data
For the sake of our illustration, we will consider the example of a simple B2C ecommerce app where users
can purchase products. Users are served by merchants that store products.
Each product is assigned a category. Merchants acquire these products from suppliers - called “vendors” - and store them
till they are sold to a customer.
Business Context
App Workflow
- Users log in and see items available at the nearest merchant.
- Users add items to a virtual shopping cart.
- Users check out the cart as a single order, which is delivered to their location.
- Each order item has a landed cost price and an effective selling price
- Effective selling price is calculated as the base selling price minus any discounts or promotions.
Key Metrics
These are the key metrics that the business is interested in:- GMV: Sum of the selling price of all orders.
- Total Margin: Sum of the margin (selling price - landed cost price) of all orders.
- Aggregations by date, merchant and product category.
Additional Complexity
- Each merchant acquires items from vendors in batches, with varying prices.
- The effective landed cost price is a weighted rolling average recalculated daily.
- Promotions are applied at the item level.
Source Tables
Let’s define the schema of the source tables as they would appear in the production database:Users
Contains information about the users of the app.| Column Name | Type | Description |
|---|---|---|
| id | VARCHAR | Primary Key |
| name | VARCHAR | Name of the user |
| VARCHAR | Email of the user | |
| lat | FLOAT | Latitude of the user |
| long | FLOAT | Longitude of the user |
| createdAt | TIMESTAMP | Time when the user was created |
| updatedAt | TIMESTAMP | Time when the user was last updated |
Merchants
Contains information about the merchants who store and sell items to users.| Column Name | Type | Description |
|---|---|---|
| merchant_id | VARCHAR | Primary Key |
| merchant_name | VARCHAR | Name of the merchant |
| geo_loc | GEOGRAPHY | Latitude/Longitude of the merchant |
| createdAt | TIMESTAMP | Time when the merchant was created |
| updatedAt | TIMESTAMP | Time when the merchant was last updated |
Items
Contains information about the items available for sale.| Column Name | Type | Description |
|---|---|---|
| item_id | VARCHAR | Primary Key |
| merchant_id | VARCHAR | Foreign Key referencing merchant_id in merchants table |
| name | VARCHAR | Name of the item |
| category | VARCHAR | Category of the item |
| price | FLOAT | Base selling price of the item |
| created_at | TIMESTAMP | Time when the item was created |
| updated_at | TIMESTAMP | Time when the item was last updated |
Promotions
Contains information about the promotions applied to items.| Column Name | Type | Description |
|---|---|---|
| promotion_id | VARCHAR | Primary Key |
| product_id | VARCHAR | Name of the item to which promotion is applied |
| discount | FLOAT | Percentage discount applied to the item |
| created_at | TIMESTAMP | Time when the promotion was created |
| updated_at | TIMESTAMP | Time when the promotion was last updated |
Inventory
Contains information about the batches of items acquired by merchants.| Column Name | Type | Description |
|---|---|---|
| inventory_id | SERIAL | Primary Key |
| merchant_id | INT | Foreign Key referencing merchant_id in merchants table |
| item_id | INT | Foreign Key referencing item_id in items table |
| qty | INT | Quantity of the item in inventory |
| date_acquired | DATE | Date when the item was acquired |
| cost | DECIMAL | Cost price of the item |
| created_at | TIMESTAMP | Time when the inventory record was created |
| updated_at | TIMESTAMP | Time when the inventory record was last updated |
Orders
Contains information about the orders placed by users.| Column Name | Type | Description |
|---|---|---|
| order_id | SERIAL | Primary Key |
| customer_id | INT | Foreign Key referencing user_id in users table |
| store_id | INT | Foreign Key referencing merchant_id in merchants table |
| date | TIMESTAMP | Date and time of the order |
| created_at | TIMESTAMP | Time when the order was created |
| updated_at | TIMESTAMP | Time when the order was last updated |
Order Items
Contains information about the items in each order.| Column Name | Type | Description |
|---|---|---|
| order_item_id | SERIAL | Primary Key |
| order_id | INT | Foreign Key referencing order_id in orders table |
| product_id | INT | Foreign Key referencing item_id in items table |
| qty | INT | Quantity of the item in the order |
| created_at | TIMESTAMP | Time when the order item was created |
| updated_at | TIMESTAMP | Time when the order item was last updated |