title: Select first day of preceding month in (DB2) SQL
body: <p>I need to check whether a given date is in the preceding month for a monthly query. I can get</p>
  
  <pre><code>CURRENT DATE - 1 MONTH
  </code></pre>
  
  <p>to compare the selected date with, but I can't assume the current date will be the first day of each month exactly. Is there a built in way to get the first day of the month without extracting the year and month and gluing it back together?</p>