SQL Default Constraints

SQL Default Constraints

Default Constraints is used to insert a default value into a column. The default value will be added to all new records, if no other value is specified.

	
create table Employee
(
e_id number(3) NOT NULL,,
e_name varchar(15),
sal number(5),
City varchar(255) DEFAULT 'Delhi',
);

In above syntax in city column by default value for city of every employee is delhi.

SQL DEFAULT Constraint on Alter Table

	
ALTER TABLE Employee
ALTER City SET DEFAULT 'delhi'

	
ALTER TABLE Employee
ALTER COLUMN City SET DEFAULT 'delhi'

	
ALTER TABLE Employee
ALTER City SET DEFAULT 'delhi'

Drop Default Constraints

	
ALTER TABLE Employee
ALTER City DROP DEFAULT

	
ALTER TABLE Employee
ALTER COLUMN City DROP DEFAULT