Mastering SQL: Creating Tables with Primary and Foreign Keys

Which SQL statement correctly creates the Exam table with a primary and foreign key?

• A. CREATE TABLE Exam (exam_id INT PRIMARY KEY, patient_id INT FOREIGN KEY)
• B. CREATE TABLE Exam (exam_id INT, exam_date DATE, patient_id INT, PRIMARY KEY (exam_id), FOREIGN KEY (patient_id))
• C. CREATE TABLE Exam (exam_id INT, PRIMARY KEY, patient_id INT)
• D. CREATE TABLE Exam (exam_id INT, patient_id INT UNIQUE)

Answer: (B)

The choice that creates the Exam table correctly, including both a primary key and a foreign key, is the one that clearly defines these constraints in the table structure. It specifies the columns to be included in the table, such as exam_id, exam_date, and patient_id, and explicitly sets exam_id as the primary key. Moreover, it establishes patient_id as a foreign key. This is crucial in relational database design, as the foreign key establishes a relationship between the Exam table and another table (presumably a Patients or similar table) where patient_id exists. This maintains referential integrity by ensuring that the patient_id in the Exam table must correspond to an existing patient in the related table. In contrast, other options either miss elements necessary for defining these keys properly or misrepresent their roles. For example, the first option attempts to designate patient_id as a foreign key but does not correctly structure the command. The third option mentions a primary key but lacks the proper syntax to define patient_id as a foreign key or even to lay out any additional constraints. The fourth option misuses the UNIQUE constraint instead of a foreign key, thus failing to create the necessary relationship between tables. Overall, the correct option provides a complete and syntactically correct definition

When it comes to database management, understanding SQL is vital, especially if you're gearing up for the Western Governors University ITEC2117 course. A significant part of that journey involves masterfully creating tables, which sounds straightforward, but there are intricacies beneath the surface. For instance, have you ever stumbled upon a question like, "Which SQL statement correctly creates the Exam table with a primary and foreign key?"

Let’s break down this question together! The options presented might look similar, but only one stands out as the clear winner. It’s a bit like ordering a coffee—sometimes, the details make all the difference. So, the right choice here is:

CREATE TABLE Exam (exam_id INT, exam_date DATE, patient_id INT, PRIMARY KEY (exam_id), FOREIGN KEY (patient_id));

Now, why is this the correct statement? Well, in this masterpiece of SQL syntax, you’ve got the exam_id uniquely identifying each exam (that’s your primary key) and the patient_id acting as a bridge to another table, usually where you find patient details. It’s as if you’re connecting the dots in a larger picture—ensuring that every exam corresponds to a real patient in your database.

Let’s Talk About the Keys

1. Primary Keys—The VIPs: Think of the primary key as the club bouncer. It ensures no two patrons (or records, in this case) can have the same identity. By defining exam_id as a primary key, you guarantee uniqueness. Every exam is distinct, and that matters!

2. Foreign Keys—Your Networking Buddies: On the flip side, the foreign key works like that friend of a friend who introduces you to new people. By setting patient_id as a foreign key, you’re creating a correlation between the Exam table and another table—most likely, the Patients table. This ensures that any patient_id in the Exam table is valid and corresponds to an actual entry in the Patients table, helping maintain your database's integrity.

What Happens When You Get It Wrong

Look closely at the other options. They might seem tempting, but they falter:

• Option A suggests a foreign key without proper structure. It’s like saying, "I’ll have the coffee without the cup."

• Option C mentions a primary key but skips the foreign key definition entirely. It’s as if you want the fancy dessert but forget the fork.

• Option D misuses the UNIQUE constraint instead of a foreign key. Instead of connecting tables, it merely ensures that values in patient_id are unique—a noble intention but missing the relational dynamic.

Pulling It All Together

So, what’s the takeaway here? Effectively using SQL to define your tables is fundamental. Not only does it lay the groundwork for your database but also facilitates robust data relations, ensuring integrity at every level. As you study for the ITEC2117 course, keep these concepts top of mind. Remember, getting comfortable with SQL statements and their nuances is essential.

Understanding primary and foreign keys will not only aid you in passing your assessments but also pave the way for advanced database design techniques down the line. So, as you gear up for your pre-assessment practice, feel free to revisit these concepts and reinforce your learning. You got this!