title: Understanding spraklyr library in sql_render() function
body: <p>There is sql_render function which translate dplyr code to SQL,
  but I cannot understand the result as SQL code.</p>
  
  <pre><code>sc &lt;- spark_connect()
  library(sparklyr)
  library(dplyr)
  iris &lt;- copy_to(sc, iris, 'iris')
  k = iris %&gt;% filter(Sepal_Length &gt; 3) %&gt;% filter(Sepal_Width &gt; 3) %&gt;% 
  select(Petal_Length, Petal_Width, Species)
  
  sql_render(k)
  </code></pre>
  
  <hr>
  
  <p> SELECT <code>Petal_Length</code> AS <code>Petal_Length</code>, <code>Petal_Width</code> AS <code>Petal_Width</code>, <code>Species</code> AS <code>Species</code>
  FROM (SELECT *
  FROM (SELECT *
  FROM <code>iris</code>
  WHERE (<code>Sepal_Length</code> > 3.0)) <code>hezmcfppjh</code>
  WHERE (<code>Sepal_Width</code> > 3.0)) <code>exwivyezte</code></p>
  
  <hr>
  
  <p>What is the 'hezmcfppjh' and 'exwivyezte' ?</p>