title: Querydsl: JPAUpdateClause with multiple sources
body: <p>I am new to Querydsl so the question might seem stupid to some of you :)</p>
  
  <p>Here is what I want to do:</p>
  
  <pre><code>QAppt qApptRqst = QAppt.apptRqst;
  QLocZip qLocZip = QLocZip.locZip;
  
  JPAQuery query = new JPAQuery(em);
  
  JPAUpdateClause upd = new JPAUpdateClause(em, qApptRqst);
  upd.where(qApptRqst.apptRqstStatusRef.apptRqstStatusCd.eq("U"),
  qApptRqst.applZip5Cd.eq(qLocZip.usZip5Cd))
     .set(qApptRqst.uscisLocation.uscisLocCd, qLocZip.uscisLocCd)
     .execute();
  </code></pre>
  
  <p>I have following exception:</p>
  
  <pre><code>"java.lang.IllegalArgumentException: Undeclared path 'locZipJuris'. Add this path as a source to the query to be able to reference it."
  </code></pre>
  
  <p>How do I use <strong>JPAUpdateClause</strong> with multiple sources?</p>