title: Mutate variables in database tables directly using dplyr
body: <p>Here is mtcars data in the MonetDBLite database file.</p>
  
  <pre><code>library(MonetDBLite)
  library(tidyverse)
  library(DBI)
  
  dbdir &lt;- getwd()
  con &lt;- dbConnect(MonetDBLite::MonetDBLite(), dbdir)
  
  dbWriteTable(conn = con, name = "mtcars_1", value = mtcars)
  
  data_mt &lt;- con %&gt;% tbl("mtcars_1")
  </code></pre>
  
  <p>I want to use dplyr mutate to create new variables and add (commit!) that to the database table? Something like </p>
  
  <pre><code>data_mt %&gt;% select(mpg, cyl) %&gt;% mutate(var = mpg/cyl) %&gt;% dbCommit(con)
  </code></pre>
  
  <p>The desired output should be same when we do:</p>
  
  <pre><code>dbSendQuery(con, "ALTER TABLE mtcars_1 ADD COLUMN var DOUBLE PRECISION")
  dbSendQuery(con, "UPDATE mtcars_1 SET var=mpg/cyl") 
  </code></pre>
  
  <p>How can do that?</p>