RE: sql join on substrings, or derived fields, giving me grief

Thanks, I've got other issues, but this "works":
with T1 as ( 
 select substr(joesd,70,30) as MessageText, 
        substr(joesd,46,6)  as MessageDate, 
        substr(joesd,52,6)  as MessageTime, 
        substr(joesd,58,10) as MessageId 
 From Zmfstuff 
 Where substr(joesd,70,30) like '7G MSGID MAP TO ID%' 
    Or substr(joesd,70,30) like '7P CRT UNDEL NOTICE OR DSN%' 
  ) 
Select Jodate, jojob, jouser, jonbr, jopgm, joobj, jolib, jombr,
       substr(joesd,70,30) as MessageText, 
       substr(joesd,46,6)  as MessageDate, 
       substr(joesd,52,6)  as MessageTime, 
       substr(joesd,58,10) as MessageId 
>From zmfstuff A join T1 on substr(joesd,46,6) = T1.MessageDate 
AND  substr(joesd,58,10) = T1.MessageID 

Rob Berendt