Given a table orders(order_id, customer_id, amount) with a foreign key on customer_id, what will happen if you try to insert an order with a customer_id that does not exist in the customers table?

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SQL - Database Design and Normalization

Given a table orders(order_id, customer_id, amount) with a foreign key on customer_id, what will happen if you try to insert an order with a customer_id that does not exist in the customers table?

AThe insert will succeed but customer_id will be set to NULL

BThe insert will succeed and create a new customer automatically

CThe insert will fail due to foreign key constraint violation

DThe insert will succeed and ignore the foreign key

Step-by-Step Solution

Solution:

Step 1: Understand foreign key enforcement
Foreign keys prevent inserting values that don't exist in the referenced table.
Step 2: Predict insert behavior
Inserting a non-existing customer_id violates the constraint, causing failure.
Final Answer:
The insert will fail due to foreign key constraint violation -> Option C
Quick Check:
Foreign key violation causes insert failure [OK]

Quick Trick: Foreign keys block inserts with invalid references [OK]

Common Mistakes:

Assuming automatic creation of referenced rows
Thinking foreign keys allow NULL silently
Believing foreign keys can be ignored on insert

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More SQL Quizzes

Given a table orders(order_id, customer_id, amount) with a foreign key on customer_id, what will happen if you try to insert an order with a customer_id that does not exist in the customers table?

Step 1: Understand foreign key enforcement

Step 2: Predict insert behavior

Final Answer:

Quick Check:

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