title: Converting string column to timestamp in BigQuery?
body: <p>I am trying to convert a column in a BQ table to timestamp. I have two string columns, one for utc_hour (string 0-23) and utc_day (string yyyymmdd) imported from a public data source. I merged the two columns to produce a string column, utc_timestamp, with strings like this - "20171208 500" . </p>
  
  <p>I need to convert that string into timestamp, and when I use </p>
  
  <pre><code>TIMESTAMP(utc_timestamp)
  </code></pre>
  
  <p>I get the error message </p>
  
  <pre><code>Invalid timestamp: '20171208 500'
  </code></pre>
  
  <p>I tried using dataprep, which also could not convert that string to a timestamp. </p>
  
  <p>How can I convert this format to a timestamp? </p>