Informix to SQL attribute constraint

I have a constraint as follows in my script & I learnt that it's Informix:

create table blaBla
{
 var_name_1 not null constraint n255_153,
 var_name_1 not null constraint n655_699,
}

I can't find an equivalent to this in SQL. I tried just typing it the same but it doesn't work. What's the equivalent in other DBMS?

via Chebli Mohamed