title: On Conflict Do Nothing in Postgres with a not-null constraint
body: <p>Is it not possible to utilize &quot;ON CONFLICT DO NOTHING&quot; to avoid inserting and violating a not-null constraint?</p>
  <p>For example...</p>
  <pre><code>INSERT INTO public.users (user, user_yob, sex) 
  SELECT mom, mom_yob, 'F' 
  FROM staging.users 
  ON CONFLICT DO NOTHING;
  </code></pre>
  <p>Produces this error and stops...</p>
  <pre><code>INSERT INTO public.users (user, user_yob, sex) SELECT mom, mom_yob, 'F' FROM staging.users ON CONFLICT DO NOTHING
  &gt; ERROR:  null value in column &quot;user&quot; violates not-null constraint
    DETAIL:  Failing row contains (0b159b81-6842-4ae7-961c-2e9cff8488b1, null, null, null, null, null, null, null, null, null, F).
  </code></pre>
  <p>Ideally, this particular insert would be ignored rather than raise the error.</p>