Re: DEFAULT NOW() AND DEFAULT USER ...
I think you should do it like this:
D_FEC_CRE TIMESTAMP DEFAULT CURRENT_TIMESTAMP
This is the only case where a non-constant expression can be used a a default value for a column, so you cannot use this for the V_USU_CRE column.
If you are migrating to MySQL 5, you can solve that with a BEFORE INSERT trigger:
create trigger bir_RGMD_GESTION
before insert on RGMD_GESTION
for each row
if new.V_USU_CRE is null then
set V_USU_CRE := SESSION_USER();
although it is not entirely equivalent: this does not distinguish between the case where the V_USU_CRE is not present in the insert statement and the ce where it is present and explicitly set to NULL. (I believe that in Oracle the latter case would in fact insert a NULL in the column as it is explicitly requested.)
You should check out Beat's comments on the right function to use for the current user bit: