title: SQL Query (or Join) for 3 tables
body: <p>first time asking a question on Stack Overflow... Amazing resource, but there's just one thing that's really baffling me as a newcomer to SQL.</p>
  
  <p>I have three tables and I would like to obtain the names of all the Mentors who are linked to Bob's students.</p>
  
  <p>Table 1: TEACHERS</p>
  
  <pre><code>================
  ID     Name
  ================
  1     Bob
  </code></pre>
  
  <p>Table 2: STUDENTS</p>
  
  <pre><code>===================================
  STUDENT_ID     Name     TEACHER_ID
  ===================================
  1              Jayne    1
  2              Billy    5
  3              Mark     2
  </code></pre>
  
  <p>Table 3: MENTOR_RELATIONSHIPS</p>
  
  <pre><code>==============================
  ID     STUDENT_ID    MENTOR_ID
  ==============================
  1      1             3
  2      2             2
  3      3             3
  </code></pre>
  
  <p>Table 4: MENTORS</p>
  
  <pre><code>=====================
  MENTOR_ID     Name  
  =====================
  1            Sally
  2            Gillian
  3            Sean
  </code></pre>
  
  <p>I would like to run a query to find all of the mentors of Bob's students.  So the mentors for all students with <code>TEACHER_ID = 1</code> </p>
  
  <p>In this case Sean would be the result.</p>
  
  <p>I know that it is something to do with Joins, or could I find this using a normal query??</p>
  
  <p>Any help is much appreciated!  Many thanks...</p>