Exceptions:
Ø NOT NULL constraint is supported for
an attribute whose data type is USER_DEFINED object, VARRAY, REF, LOB.
Ø NOT NULL, FOREIGN KEY, and REF
constraints are supported on a column of type REF.
Ø NOT NULL Constraint:
Ø A NOT NULL constraint prohibits a
column from containing NULL values.
Ø NOT NULL should be defined only at
column level.
Ø The default constraint if not
specified is NULL constraint.
Ø To satisfy the rule, every row in
the table must contain a value for the column.
Restrictions:
Ø NULL or NOT NULL cannot be specified
as view constraints.
Ø NULL or NOT NULL cannot be specified
for an attribute of an object.
Syntax:
·
Create Table <table_name>
(
Column_name1 <data
type>(width) NOT NULL,
Column_name2<data
type>(width)
Contraint consname NOT
NULL,
Column_nameN <data
type>(width)
);
Illustration:
·
Create Table Students
(
Studno
number(6)
CONSTRAINT
StudnoNN NOT NULL,
StudName
varchar2(25)
CONSTRAINT
StudNameNN NOT NULL,
CourseName
varchar2(25)
CONSTRAINT
CourseNameNN NOT NULL,
JoinDate
Date NOT NULL
);