title: update select union with the pi () function Oracle SQL
body: <p>I want to use the pi function within an update statement. I have OracleDeveloper Version 3.2.10.09</p>
  
  <pre><code>update a_oracle_table
      set test_n = sqrt(a)/pi
      from 
          select * from a_oracle_table
          where a is not null and a &gt;0
          union all
          select pi() from dual;
  </code></pre>
  
  <p><code>select pi() from dual</code> produces error <code>invalid identifier</code>.</p>
  
  <p>How can I use pi in my update statement?</p>