title: Concat rows in Postgres
body: <p>Given is a Postgres table like this</p>
  
  <pre><code>nummer  vorname    name        cash
  ------|-----------|-----------|-----
  1       paul       smith       500
  2       andy       london      700
  2       mike       dover       700
  3       clara      winchester  200
  </code></pre>
  
  <p>To query this table my sql looks like this right know:</p>
  
  <pre><code>SELECT 
    nummer,
    vorname,
    name,  
    cash as total
  FROM 
    data.myTable
  GROUP BY
    nummer, 
    name,
    vorname,
    cash
  ORDER BY
    nummer; 
  </code></pre>
  
  <p>Is it possible to concat the two rows where <code>nummer</code> is the same (in this case <code>2</code>). 
  Means my output should look like this (cash will also have the same values if the numbers are equal):</p>
  
  <pre><code>nummer  vorname    name        cash
  ------|-----------|-----------|-----
  1       paul       smith       500
  2       andy       london      700
          mike       dover       
  3       clara      winchester  200
  </code></pre>