Using a preprocessor for constants in SQL

Hi all

When defining records with varchar entries (and at some other places)
something like constants would be useful. They could look something like
this:

DEFINE short = 20;
DEFINE long = 2000;

CREATE TABLE example (
short_string varchar (short),
long_string varchar (long),
long_string2 varchar (long)
);
[...]
CREATE TABLE example200 (
short_name varchar (short),
long_name varchar (long)
);

Like this you could easily change values between test setup and final
deployment. Is there anything like this or is there some elegant way to
achieve this? Or do you all use some sort of preprocessors?

Arthur