SQL & PL/SQL

Hey guys I seem to have a mental block here. I have two sql statements. I would like the second to run only if the first sql statement is null.I know i can potentially use PLsql but would really like to see if i can do this with straight up sql. Your responses are very very appreciated.
here is the first sql

  Select     ft.fund_code, 
             ft.orgn_code, 
             ft.acct_code, 
             ft.amount, 
             fb.owner_pidm, 
             ft.prog_code      
      from ftrbremb fb , ftcractg ft
      where fb.doc_code = 'TR000038'
      and fb.ftpbport_id = ft.ftpbport_id

second sql statement

     Select ft.fund_code, 
             ft.orgn_code, 
             ft.acct_code, 
             ft.amount, 
             fb.owner_pidm, 
             ft.prog_code      
      from ftrbremb fb , ftcractg ft, ftprexps fx
      where fb.doc_code = 'TR000038'
      --and fb.ftpbport_id = ft.ftpbport_id
      and fx.ftrbremb_id = fb.id
      and ft.ftprexps_id = fx.id;

How can i combine these two statements together so that when the first one is null the second one runs. As a bonus i like to get just the first row as well.
Any help would greatly appreciated. I tried to accomplish with case statement but it just dosent seem to be working for me.
Thanks