Not Null

NOT NULL (Domain Integrity Constraint):-
            When column is defined  as Not Null, then that column becomes a mandatory column. It implies that a value must be entered into the column if the record is to be accepted for storage in the table. The not null constraint is can only be applied at column leval.
Syntax:-                      columname datatype(size)
Ex:-                 create table vision1(eno number(5) not null,na varchar2(20),
sal number(5));
                        1)insert into vision1 values(100,’prasad’,3200);

• 2)insert into vision1 (na,sal) values(‘reshu’,2100);

note:- the 2nd query shows an error because the not null column is not included in the query.

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