title: PostgreSQL Concat 2 numbers gives me error
body: <p>I'm trying to concat 2 numbers from two different columns, those are chain_code and shop_code.</p>
  
  <p><img src="https://i.stack.imgur.com/uCuJW.png" alt="enter image description here"></p>
  
  <p>I tried this:</p>
  
  <pre><code>SELECT CONCAT(`shop_code`, `shop_code`) AS myid FROM {table}
  </code></pre>
  
  <p>But I get an error:</p>
  
  <pre><code>ERROR:  operator does not exist: ` integer
  LINE 1: SELECT CONCAT(`shop_code`, `shop_code`) AS myid FROM...
                    ^
  HINT:  No operator matches the given name and argument type(s). You might need to add explicit type casts.
  </code></pre>
  
  <p>I even tried to convert it to string but couldn't <code>... CONCAT(to_char(chain_code, '999')...) ...</code> but it says there is no such a function called 'to_sting' (found on <a href="http://www.postgresql.org/docs/9.3/static/functions-formatting.html" rel="nofollow noreferrer">PostgreSQL Documentation</a>)</p>