[Solved] A foreign key constraint fails to create with error "Cannot add foreign key constraint". Which fix is most appropriate?ALTER TABLE Orders ADD FOREIGN KEY (CustomerID) REFERENCES Customers(CustomerID); | SQL

SQL - Table Constraints

A foreign key constraint fails to create with error "Cannot add foreign key constraint". Which fix is most appropriate?
ALTER TABLE Orders ADD FOREIGN KEY (CustomerID) REFERENCES Customers(CustomerID);

AChange Orders.CustomerID to VARCHAR if Customers.CustomerID is INT.

BEnsure Customers.CustomerID is a primary or unique key.

CRemove the foreign key from Orders.

DDelete all rows from Orders before adding the constraint.

Step-by-Step Solution

Solution:

Step 1: Check referenced key requirements
The referenced column must be a primary or unique key.
Step 2: Apply fix
Ensuring Customers.CustomerID is primary or unique allows foreign key creation.
Final Answer:
Ensure Customers.CustomerID is a primary or unique key. -> Option B
Quick Check:
Referenced key must be unique or primary [OK]

Quick Trick: Referenced column must be unique or primary key [OK]

Common Mistakes:

MISTAKES

Changing data types incorrectly
Deleting data unnecessarily
Removing foreign key instead of fixing parent key

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More SQL Quizzes

A foreign key constraint fails to create with error "Cannot add foreign key constraint". Which fix is most appropriate?

Step 1: Check referenced key requirements

Step 2: Apply fix

Final Answer:

Quick Check:

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