select dochead.*, trim(substring(imp_link.imp_extid from 7 for 10)) GREXTID from dochead 
join imp_link on dochead.WREPORTINGGROUP1ID = IMP_LINK.WGROUPID and IMP_LINK.IMP_SOURCEID = <@SOURCEID@>
join imp_link b on dochead.WDOCID = b.WDOCID and b.IMP_SOURCEID = <@SOURCEID@>
where dochead.WDOCID = <@KEY@>
 order by 1
  