Q:

MySQL Command Line Client: Selecting records from a table which links two other tables

I have three tables. Two of them are separate irrelevant tables (students and subjects), the third (entries) is one which links them both with foreign keys (student_id and subject_id). 
Here are all the tables with the records:
students:
+------------+------------+-----------+---------------------+----------------------+
| student_id | first_name | surname   | email               | reg_date             |
+------------+------------+-----------+---------------------+----------------------+
|          1 | Emma       | Harvey    | emmah@gmail.com    | 2012-10-14  11:14:13 |
|          2 | Daniel     | ALexander | daniela@hotmail.com | 2014-08-19  08:08:23 |
|          3 | Sarah      | Bell      | sbell@gmail.com     | 1998-07-04  13:16:32 |
+------------+------------+-----------+---------------------+--------------- ------+

subjects:
+------------+--------------+------------+----------------+
| subject_id | subject_name | exam_board | level_of_entry |
+------------+--------------+------------+----------------+
|          1 | Art          | CCEA       | AS             |
|          2 | Biology      | CCEA       | A              |
|          3 | Computing    | OCR        | GCSE           |
|          4 | French       | CCEA       | GCSE           |
|          5 | Maths        | OCR        | AS             |
|          6 | Chemistry    | CCEA       | GCSE           |
|          7 | Physics      | OCR        | AS             |
|          8 | RS           | CCEA       | GCSE           |
+------------+--------------+------------+----------------+    

entries:
+----------+---------------+---------------+------------+
| entry_id | student_id_fk | subject_id_fk | entry_date |
+----------+---------------+---------------+------------+
|        1 |             1 |             1 | 2012-10-15 |
|        2 |             1 |             4 | 2011-09-21 |
|        3 |             1 |             3 | 2015-08-10 |
|        4 |             2 |             6 | 1992-07-13 |
|        5 |             3 |             7 | 2013-02-12 |
|        6 |             3 |             8 | 2016-01-14 |
+----------+---------------+---------------+------------+

I want to know how to select all the first_names of the students in the students table, who have entries with a with the OCR exam_board from the subjects table, using the entries table.
I'm sure it has to do with joins, but which one to use and the general syntax of it, I don't know.
I'm generally awful at explaining things, so sorry if these doesn't make a ton of sense and if I've missed out something important. I'll gladly go into more specifics if necessary.
I've got an answer, but what I was looking for as the output was this:
+------------+
| first_name |
+------------+
| Emma       |
| Sarah      |
+------------+

A:

You should use INNER JOINS in your query, like:
SELECT      students.first_name
    FROM    students
INNER JOIN  entries
        ON  entries.student_id_fk = students.student_id
INNER JOIN  subjects
        ON  subjects.subject_id = entries.subject_id_fk
    WHERE   subjects.exam_board = 'OCR';

This query will join the tables on the matching key values, select the ones with exam_board OCR and return the student first_name.

