Solution:Step 1: Understand UNIQUE on PersonID in PassportThe UNIQUE constraint means no two rows in Passport can have the same PersonID, so one person links to at most one passport.Step 2: Analyze relationship enforcedSince Passport has a foreign key to Person and PersonID is unique, each passport

[Solved] Given these tables:CREATE TABLE Person ( PersonID INT PRIMARY KEY, Name VARCHAR(50) );... | SQL

SQL - Table Relationships

Given these tables:

CREATE TABLE Person (
  PersonID INT PRIMARY KEY,
  Name VARCHAR(50)
);

CREATE TABLE Passport (
  PassportID INT PRIMARY KEY,
  PersonID INT UNIQUE,
  Number VARCHAR(20),
  FOREIGN KEY (PersonID) REFERENCES Person(PersonID)
);

What does the UNIQUE constraint on PersonID in Passport ensure?

AEach person can have multiple passports

BEach passport belongs to exactly one person, and each person has at most one passport

CPersonID can be null in Passport

DPassportID can be duplicated

Step-by-Step Solution

Solution:

Step 1: Understand UNIQUE on PersonID in Passport
The UNIQUE constraint means no two rows in Passport can have the same PersonID, so one person links to at most one passport.
Step 2: Analyze relationship enforced
Since Passport has a foreign key to Person and PersonID is unique, each passport belongs to one person, and each person can have only one passport.
Final Answer:
Each passport belongs to exactly one person, and each person has at most one passport -> Option B
Quick Check:
Unique foreign key = one-to-one link [OK]

Quick Trick: UNIQUE foreign key means one-to-one link [OK]

Common Mistakes:

MISTAKES

Thinking one person can have many passports
Ignoring UNIQUE constraint effect
Assuming null allowed without checking

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Given these tables:

Step 1: Understand UNIQUE on PersonID in Passport

Step 2: Analyze relationship enforced

Final Answer:

Quick Check:

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