Normalization in Database Design | Dataford Interview Questions

What is the importance of normalization in database design?

Use the normalized tables provided to demonstrate how related entities can be combined without storing repeated customer or order data. Write a query that summarizes customer purchasing activity.

Output

One row per customer, including customers with no orders
Columns: customer_id, customer_name, order_count, and total_spent
Count each order once and treat customers without line items as having zero spending
Order by customer_id ascending

Schema

customers

Column	Type	Description
customer_idPK	INT	Unique customer identifier
customer_name	VARCHAR(100)	Customer's display name

orders

Column	Type	Description
order_idPK	INT	Unique order identifier
customer_id	INT	Customer who placed the order
order_date	DATE	Date the order was placed
order_status	VARCHAR(20)	Current order status

order_items

Column	Type	Description
order_item_idPK	INT	Unique order line identifier
order_id	INT	Order containing the line item
quantity	INT	Number of units purchased
unit_price	DECIMAL(10,2)	Price per unit at purchase time

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Problem