title: Add hours to timestamp in Netezza based on other column
body: <p>I'm working in a Netezza SQL database. I have 2 columns:</p>
  
  <ul>
  <li>DATETIME1: has the timestamp of transaction at UTC time</li>
  <li>TIME_OFFSET: is an integer, showing the offset of the users' time zone from UTC. For example, users in UTC+1 have value 1.</li>
  </ul>
  
  <p>What I would like to do is add the <code>TIME_OFFSET</code> column to the <code>DATETIME1</code> column as an hour.</p>
  
  <p>I created the following reproducible example:</p>
  
  <pre><code>SELECT *
  FROM ADMIN.INTEGRAL_ADSCIENCE_1845
  
  WITH my_table AS (
  SELECT TIMESTAMP('2017-06-01 08:01:45') AS datetime1,
      1 AS time_offset
  UNION 
  SELECT TIMESTAMP('2017-06-01 08:03:45') AS datetime1,
      2 AS time_offset
  )
  SELECT
      DATETIME1,
      TIME_OFFSET,
      DATETIME1 + TIME_OFFSET AS simple_add,
      DATETIME1 + INTERVAL '1 hour' AS add_one_hour
  FROM my_table;
  </code></pre>
  
  <p>This creates the following output:</p>
  
  <pre><code>+---------------------+-------------+------------+---------------------+
  |      DATETIME1      | TIME_OFFSET | SIMPLE_ADD |    ADD_ONE_HOUR     |
  +---------------------+-------------+------------+---------------------+
  | 2017-06-01 08:01:45 |           1 | 2017-06-02 | 2017-06-01 09:01:45 |
  | 2017-06-01 08:03:45 |           2 | 2017-06-03 | 2017-06-01 09:03:45 |
  +---------------------+-------------+------------+---------------------+
  </code></pre>
  
  <p>But what I would like to have is adding 1 hour to first row and 2 hours to second row.</p>
  
  <p>I'm aware of the mysql <code>date_add()</code> function, but I'm limited to Netezza unfortunately.</p>