update mscrm_config.dbo.systemuser set mscrm_config.dbo.systemuser.defaultorganizationid = 
      (select sub.organizationid from systemuserbase sub, 
       mscrm_config.dbo.systemuserorganizations csuo
       where sub.systemuserid = csuo.crmuserid and 
       csuo.userid = mscrm_config.dbo.systemuser.id)
where 1 = 
      (select count(*) from systemuserbase sub, 
       mscrm_config.dbo.systemuserorganizations csuo
       where sub.systemuserid = csuo.crmuserid and 
       csuo.userid = mscrm_config.dbo.systemuser.id and
    sub.domainname = 'domain\username')
