title: Joining by multiple columns with stringdist_join
body: <p>I have two dataframes, where column <code>x</code> can have typos and column <code>y</code> is always correct.
  I can't figure out why joining by multiple columns with <code>stringdist</code> gives these pairs:</p>
  <pre><code>library(dplyr)
  library(fuzzyjoin)
  a &lt;- data.frame(x = c(&quot;season&quot;, &quot;season&quot;, &quot;season&quot;, &quot;package&quot;, &quot;package&quot;), y = c(&quot;1&quot;,&quot;2&quot;, &quot;3&quot;, &quot;1&quot;,&quot;6&quot;))
  
  b &lt;- data.frame(x = c(&quot;season&quot;, &quot;seson&quot;, &quot;seson&quot;, &quot;package&quot;, &quot;pakkage&quot;), y = c(&quot;1&quot;,&quot;2&quot;, &quot;3&quot;, &quot;2&quot;,&quot;6&quot;))
  
  c &lt;- a %&gt;%
    stringdist_left_join(b, by = c(&quot;x&quot;, &quot;y&quot;), max_dist = c(1,0))
  
        x.x y.x     x.y  y.y
  1  season   1  season    1
  2  season   1   seson    2
  3  season   1   seson    3
  4  season   2   seson    2
  5  season   3  season    1
  6  season   3   seson    2
  7  season   3   seson    3
  8 package   1 package    2
  9 package   6    &lt;NA&gt; &lt;NA&gt;
  </code></pre>
  <p>I would like to get</p>
  <pre><code>      x.x y.x     x.y  y.y
  1  season   1  season    1
  2  season   2   seson    2
  3  season   3   seson    3
  4 package   1    &lt;NA&gt; &lt;NA&gt;
  5 package   6 pakkage    6
  </code></pre>