Given entities Customer(cust_id, name), Order(order_id, date), and a one-to-one relationship where each order has exactly one customer, how should tables be designed?

hard📝 Application Q9 of 15

SQL - Table Relationships

Given entities Customer(cust_id, name), Order(order_id, date), and a one-to-one relationship where each order has exactly one customer, how should tables be designed?

AMerge Customer and Order into one table

BAdd cust_id as foreign key in Order table with UNIQUE constraint

CCreate separate table for the relationship

DAdd order_id as foreign key in Customer table without UNIQUE

Step-by-Step Solution

Solution:

Step 1: Understand one-to-one relationship mapping
One-to-one can be represented by placing foreign key with UNIQUE constraint in one table.
Step 2: Choose correct foreign key placement
Order table should have cust_id as foreign key with UNIQUE to ensure one-to-one mapping.
Final Answer:
Add cust_id as foreign key in Order table with UNIQUE constraint -> Option B
Quick Check:
One-to-one FK with UNIQUE = Add cust_id as foreign key in Order table with UNIQUE constraint [OK]

Quick Trick: One-to-one uses FK with UNIQUE constraint [OK]

Common Mistakes:

MISTAKES

Omitting UNIQUE constraint
Placing FK in wrong table
Creating unnecessary relationship table

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More SQL Quizzes

Given entities Customer(cust_id, name), Order(order_id, date), and a one-to-one relationship where each order has exactly one customer, how should tables be designed?

Step 1: Understand one-to-one relationship mapping

Step 2: Choose correct foreign key placement

Final Answer:

Quick Check:

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