SUBSTR without explicitly coding the length parm - response (1) by ulrich

I can't reproduce the issue.

select top 100
       substring(myvar from 4),
       substr(myvar,4),
       substr(myvar,14,CHARACTER_LENGTH(myvar))
from mytbl;

but as you can see above you don't need to specify the thrid parameter for substr and substring - check the different syntax in the docu.
So I guess this is what you are looking for?