title: rewrite query in orden to avoid some records
body: <p>I dont know how to rewrite the the query in order to avoid records with ISPRIMARY = 0. In other words the values allowed must be ISPRIMARY = 1 and ISPRIMARY = NULL. </p>
  
  <p>The query is the next:</p>
  
  <pre><code>select 
    S.assetnum, S.description, S.serialnum,
    S.epp_codactfij, S.location, L.description,
    S.EPP_NUMCONTRATO, S.PURCHASEPRICE, U.personid, U.isprimary
  from maximo.asset S 
  left join maximo.locations L on S.location=L.location
  left join maximo.assetusercust U on S.assetnum=U.assetnum
  where 
  S.siteid ='TI'
  order by S.assetnum
  </code></pre>