title: Select documents where one array of an array matches a condition
body: <p>I have the following document :</p>
  <pre><code>{
    &quot;key&quot;: [
      [
        &quot;FOO&quot;,
        &quot;BAR&quot;
      ],
      [
        &quot;FOO&quot;,
        &quot;BAZ&quot;
      ]
    ]
  }
  </code></pre>
  <p>I want to retrieve this document when at least one of the array from the <code>key</code> array contains 100% of some values.</p>
  <p>Exemples :</p>
  <pre><code>+--------------+----------------+
  | Given values | Should Match ? |
  +--------------+----------------+
  | FOO          | Yes            |
  | BAR          | Yes            |
  | BAZ          | Yes            |
  | FOO, BAR     | Yes            |
  | FOO, BAZ     | Yes            |
  | BAR, BAZ     | No             |
  +--------------+----------------+
  </code></pre>
  <p>From the documentation, it looks like using the <code>$elemMatch</code> and <code>$all</code> operator could work, but it doesn't (the following returns nothing) :</p>
  <pre><code>{
    &quot;key&quot;: {
      &quot;$elemMatch&quot;: {
        &quot;$all&quot;: [
          &quot;FOO&quot;
        ]
      }
    }
  }
  </code></pre>
  <p>Playground : <a href="https://mongoplayground.net/p/BtqWjoUkASs" rel="nofollow noreferrer">https://mongoplayground.net/p/BtqWjoUkASs</a></p>
  <p>To summarize, I want to run the <code>$all</code> operator on each of the arrays contained in an other array.</p>