The correct answer is ON DELETE CASCADE on the foreign key constraint for Orders.CustomerID. This is because ON DELETE CASCADE is a referential action that automatically deletes all child rows in the Orders table whenever the corresponding parent row in the Customers table is removed, ensuring data integrity without manual intervention or additional triggers. On the Microsoft Azure Data Fundamentals DP-900 exam, this concept tests your understanding of foreign key constraints and referential integrity in Azure SQL Database, often appearing in scenario-based questions about maintaining consistent relationships between tables. A common trap is confusing ON DELETE CASCADE with ON UPDATE CASCADE or assuming triggers are required, but the key is that cascade handles deletes automatically at the database level. Memory tip: think "Cascade = Chain Reaction" — when the parent goes, the children follow.
DP-900 Practice Question: Identify considerations for relational data on Azure
This DP-900 practice question tests your understanding of identify considerations for relational data on azure. Match the stated requirement to the specific cloud service, access model, or configuration option — many options are valid in isolation but not for this scenario. After answering, compare your reasoning against the explanation and wrong-answer breakdown below. Once you have made your selection, read the full explanation to reinforce the concept and understand why each distractor is designed to mislead on exam day.
A company uses Azure SQL Database for an order processing system. The Orders table has columns: OrderID (PK), CustomerID, OrderDate, TotalAmount. The Customers table has CustomerID (PK), Name, Email. The database administrator wants to ensure that when a customer record is deleted, all orders for that customer are also automatically deleted. Which database constraint should be implemented?
Answer the question above first, then reveal the full breakdown to understand why each option is right or wrong.
Correct answer & explanation
✓
ON DELETE CASCADE on Orders.CustomerID
Option B is correct because ON DELETE CASCADE on the foreign key (Orders.CustomerID) automatically deletes all child rows in the Orders table when the parent row in the Customers table is deleted. This ensures referential integrity without requiring additional code or triggers, and is the standard SQL mechanism for cascading deletes in Azure SQL Database.
Key principle: Answer the scenario, not the keyword: identify the specific constraint before choosing the most familiar-sounding option.
Answer analysis
Option-by-option breakdown
For each option: why learners choose it and why it is or isn't the right answer here.
✗
ON DELETE SET NULL on Orders.CustomerID
Why it's wrong here
SET NULL would set the CustomerID in Orders to NULL instead of deleting the orders, which may leave orphaned data.
✓
ON DELETE CASCADE on Orders.CustomerID
Why this is correct
CASCADE automatically deletes matching rows in the Orders table when the referenced Customer is deleted.
Related concept
Read the scenario before looking for a memorised answer.
✗
ON UPDATE CASCADE on Customers.CustomerID
Why it's wrong here
ON UPDATE CASCADE applies when a parent key value is updated, not when it is deleted.
✗
A trigger on Customers table
Why it's wrong here
While a trigger can achieve the same result, using a declarative foreign key constraint is simpler, more efficient, and recommended.
Common exam traps
Common exam trap: answer the scenario, not the keyword
The trap here is that candidates often confuse ON DELETE CASCADE with ON UPDATE CASCADE, mistakenly thinking that updating a primary key is the same as deleting a record, or they incorrectly assume that a trigger is always required for cascading operations when a declarative constraint is available.
Detailed technical explanation
How to think about this question
Under the hood, ON DELETE CASCADE is implemented as a foreign key constraint that uses the database engine's internal referential integrity mechanism to automatically generate and execute DELETE statements on child rows when the parent row is deleted. In Azure SQL Database, this is handled at the storage engine level, ensuring atomicity—if the parent delete fails, all cascaded deletes are rolled back. A real-world scenario where this matters is in an order processing system with millions of rows: using a trigger instead of CASCADE could cause deadlocks or slower performance because triggers execute row-by-row, whereas CASCADE is optimized for batch operations.
KKey Concepts to Remember
Read the scenario before looking for a memorised answer.
Find the constraint that changes the correct option.
Eliminate answers that are true in general but not in this case.
TExam Day Tips
→Watch for words such as best, first, most likely and least administrative effort.
→Review why wrong options are wrong, not only why the correct option is correct.
Key takeaway
Answer the scenario, not the keyword: identify the specific constraint before choosing the most familiar-sounding option.
Real-world example
How this comes up in practice
A cloud solutions architect for a retail company is evaluating services for a new workload. The correct answer here reflects best practice for the specific scenario described — not a general cloud recommendation. Answer the scenario, not the keyword: identify the specific constraint before choosing the most familiar-sounding option. Cloud exam questions reward reading the constraint carefully: the same technology can be right or wrong depending on the use case.
Related glossary terms
Concepts from this question explained
These glossary pages explain the core terms tested in this DP-900 question in full detail.
Identify considerations for relational data on Azure — This question tests Identify considerations for relational data on Azure — Read the scenario before looking for a memorised answer..
What is the correct answer to this question?
The correct answer is: ON DELETE CASCADE on Orders.CustomerID — Option B is correct because ON DELETE CASCADE on the foreign key (Orders.CustomerID) automatically deletes all child rows in the Orders table when the parent row in the Customers table is deleted. This ensures referential integrity without requiring additional code or triggers, and is the standard SQL mechanism for cascading deletes in Azure SQL Database.
What should I do if I get this DP-900 question wrong?
Identify which exam domain this question belongs to, review the core concept, then practise similar questions from the same domain.
What is the key concept behind this question?
Read the scenario before looking for a memorised answer.
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