title: SQL - Apply where conditions to multiple rows
body: <p>The question title might be a bit unclear, so I explain the situation: </p>
  
  <p>I have a table languages</p>
  
  <pre><code>candidateprofile_id, language
  =================================
  1                      de
  1                      fr
  1                      en
  2                      de
  </code></pre>
  
  <p>Which lists the languages a candidate is able to speak in seperate records.</p>
  
  <p>The second table is language_proficiencies</p>
  
  <pre><code>candidateprofile_id, proficiency_code
  ====================================
  1                      C2
  1                      B1
  1                      C1
  2                      C2
  </code></pre>
  
  <p>Which lists the skill level candidates have for each language.</p>
  
  <p>Now I want to select the IDs of all candidates, that speak a set of given languages with a certain proficiency. </p>
  
  <p>For example, all candidates who speak german/de at C2 level, french/fr at B1 level and english/en at C1 level. </p>
  
  <p>How can I achieve this?</p>