[Solved] Consider these tables:CREATE TABLE Orders (OrderID INT PRIMARY KEY, CustomerID INT, FOREIGN KEY (CustomerID) REFERENCES Customers(CustomerID));CREATE TABLE Customers (CustomerID INT PRIMARY KEY, Name... | SQL

SQL - Table Constraints

Consider these tables:
CREATE TABLE Orders (OrderID INT PRIMARY KEY, CustomerID INT, FOREIGN KEY (CustomerID) REFERENCES Customers(CustomerID));
CREATE TABLE Customers (CustomerID INT PRIMARY KEY, Name VARCHAR(50));
What will happen if you delete a customer who has orders, without specifying ON DELETE CASCADE?

AThe delete succeeds and sets CustomerID in orders to NULL.

BThe customer is deleted and orders remain with invalid CustomerID.

CThe customer is deleted and orders are automatically deleted.

DThe delete fails due to foreign key constraint.

Step-by-Step Solution

Solution:

Step 1: Understand foreign key delete behavior
Without ON DELETE CASCADE, deleting a parent referenced by child rows is blocked.
Step 2: Check delete on customer with orders
Since orders reference the customer, delete fails to prevent orphaned records.
Final Answer:
The delete fails due to foreign key constraint. -> Option D
Quick Check:
Delete parent with children = blocked without CASCADE [OK]

Quick Trick: Delete blocked if child rows exist without CASCADE [OK]

Common Mistakes:

MISTAKES

Assuming delete cascades automatically
Thinking child foreign keys become NULL automatically
Believing delete succeeds leaving invalid references

Master "Table Constraints" in SQL

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More SQL Quizzes

Consider these tables:

Step 1: Understand foreign key delete behavior

Step 2: Check delete on customer with orders

Final Answer:

Quick Check:

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