Add constraint for lowerlimit <= upperlimit
create table salgrades
( grade NUMBER(2) constraint S_PK primary key
, lowerlimit NUMBER(6,2) constraint S_LOWER_NN not null
constraint S_LOWER_CHK check (lowerlimit >= 0)
, upperlimit NUMBER(6,2) constraint S_UPPER_NN not null
, bonus NUMBER(6,2) constraint S_BONUS_NN not null
, constraint S_LO_UP_CHK check
(lowerlimit <= upperlimit)
) ;