Which of the following is the correct syntax to add a FOREIGN KEY constraint to an existing table Orders referencing Customers(CustomerID)?

easy📝 Syntax Q12 of 15

SQL - Table Constraints

Which of the following is the correct syntax to add a FOREIGN KEY constraint to an existing table Orders referencing Customers(CustomerID)?

AALTER TABLE Orders ADD FOREIGN KEY (CustomerID) REFERENCES Customers(CustomerID);

BALTER TABLE Orders ADD PRIMARY KEY (CustomerID) REFERENCES Customers(CustomerID);

CALTER TABLE Orders ADD FOREIGN KEY CustomerID REFERENCES Customers(CustomerID);

DALTER TABLE Orders ADD FOREIGN KEY (CustomerID) TO Customers(CustomerID);

Step-by-Step Solution

Solution:

Step 1: Recall correct ALTER TABLE syntax for FOREIGN KEY
The correct syntax uses: ALTER TABLE table_name ADD FOREIGN KEY (column) REFERENCES other_table(column);
Step 2: Check each option
ALTER TABLE Orders ADD FOREIGN KEY (CustomerID) REFERENCES Customers(CustomerID); matches the correct syntax exactly. Options A, B, and C have syntax errors or wrong keywords.
Final Answer:
ALTER TABLE Orders ADD FOREIGN KEY (CustomerID) REFERENCES Customers(CustomerID); -> Option A
Quick Check:
Correct ALTER TABLE FOREIGN KEY syntax = D [OK]

Quick Trick: Use ADD FOREIGN KEY (col) REFERENCES table(col) syntax [OK]

Common Mistakes:

MISTAKES

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