Consider a database name "db_name" whose attributes are intern_id (primary key), subject, subject_value.
Intern_id = {1, 2, 3, 4, 5, 6}
Subject = {sql, oop, sql, oop, c, c++}
Subject_value = {0, 0, 1, 1, 2, 2, 3, 3}
If these are one to one relation then what will be the output of the following MySQL statement?

SELECT intern_id
FROM db_name
WHERE subject IN (SELECT subject FROM db_name WHERE subject_value = 3);

Solution (By Examveda Team)

This question is about how to use SQL to find specific data in a database. Let's break it down:
* The Database: We have a database called "db_name" that stores information about interns. Each intern has an ID number (intern_id), a subject they are studying, and a subject_value (which could represent a grade, score, or some other value).
* One-to-One Relationship: This means each intern has only one subject assigned to them.
* The SQL Statement: The code you see is a MySQL query. It's asking the database to do the following:
1. SELECT intern_id: Find the intern IDs.
2. FROM db_name: Look in the "db_name" database.
3. WHERE subject IN (SELECT subject FROM db_name WHERE subject_value = 3): This part is important! It says, "Find the interns whose subject is the same as the subjects that have a subject_value of 3."
* Finding the Answer:
1. Look at the subject_value column. The values 3 appear for the subjects "c" and "c++".
2. Now, look at the subject column and find the intern_ids associated with "c" and "c++". These are intern_ids 5 and 6.
* The Correct Answer: The output of the SQL statement will be {5, 6}, because these are the intern IDs corresponding to the subjects with a subject_value of 3.
So the correct answer is Option A: {5, 6}