Consider a database name "db_name" whose attributes are intern_id (primary key), subject.
Intern_id = {1, 2, 3, 4, 5, 6}
Subject = {sql, oop, sql, oop, c, c++}
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 (c, c++, oop, SQL);

Solution (By Examveda Team)

This question is about understanding how MySQL queries work with a database and its attributes. Here's a breakdown of the concepts:
1. Database and Attributes:
Imagine a database like a spreadsheet with rows (interns) and columns (information about each intern). In this case, our database "db_name" has two columns:
- intern_id: A unique number for each intern (like their employee ID).
- subject: The subject they are studying (like SQL or OOP).
2. One-to-One Relation:
A one-to-one relation means that each intern can only be associated with *one* subject, and each subject can only be associated with *one* intern. This is like saying each student can only take one major, and each major can only be taken by one student.
3. MySQL Query:
The query `SELECT intern_id FROM db_name WHERE subject IN (c, c++, oop, SQL);` is asking MySQL to:
- SELECT the `intern_id` column.
- FROM the `db_name` database.
- WHERE the `subject` column is one of the values in the list (`c`, `c++`, `oop`, `SQL`).
4. Finding the Answer:
Now, let's look at the provided data:
- Intern ID 1 and 2 are associated with `sql` and `oop` respectively.
- Intern ID 3 is associated with `sql`.
- Intern ID 4 is associated with `oop`.
- Intern ID 5 is associated with `c`.
- Intern ID 6 is associated with `c++`.
Because of the one-to-one relationship, only interns with `c`, `c++`, `oop`, and `sql` will be returned.
Therefore, the output of the query will be: {1, 2, 3, 4, 5, 6} So the correct answer is: Option A: {5, 6}