In the following SQL query, what does "person_id" stands for?

CREATE TABLE person
(person_ id SMALLINT UNSIGNED,
fname VARCHAR(20),
lname VARCHAR(20),
CONSTRAINT pk_person PRIMARY KEY (person_id));

Solution (By Examveda Team)

This question is asking you to identify what "person_id" represents within the given SQL code. The code creates a table named "person" with several columns:

* person_id: This column stores a unique identifier for each person in the table. It is declared as SMALLINT UNSIGNED, meaning it can hold small integer values without negative signs.
* fname: This column stores the first name of each person. It is declared as VARCHAR(20), meaning it can hold strings of up to 20 characters.
* lname: This column stores the last name of each person. It is also declared as VARCHAR(20).

The code also includes a constraint called pk_person, which is a primary key constraint applied to the person_id column.

A primary key is a special type of key in a database that uniquely identifies each row in a table. Here's why "person_id" is the primary key:

* Unique Identification: Each person must have a distinct "person_id", ensuring that no two rows have the same value.
* Data Integrity: The primary key constraint enforces this uniqueness, preventing duplicate entries and maintaining data consistency.

Therefore, the correct answer is Option D: Primary key.

Let's look at the other options and why they're incorrect:

* Option A: Normal attribute of the table - While "person_id" is an attribute of the table, it's not just a normal attribute because of its unique identification role.
* Option B: Super key - A super key is any set of attributes that can uniquely identify a row, but a primary key is the minimal set of attributes that can do so.
* Option C: Composite key - A composite key is a primary key consisting of multiple columns. In this case, "person_id" is a single-column primary key.