DEFAULT Constraint IN SQL
DEFAULT Constraint
  1. The DEFAULT constraint is used to insert a default value into a column.
  2. The default value will be added to all new records, if no other value is specified.


How to create DEFAULT Constraint on TABLE in SQL:- The following SQL creates a DEFAULT constraint on the "Email" column when the "tblEmployees" table is created:
  

CREATE TABLE tblEmployees
(
EmpID INT PRIMARY KEY,
EmpName VARCHAR(100),
Address varchar(200),
MobileNo bigint,
Email NVARCHAR(200) DEFAULT 'sa@gmail.com'
)




The DEFAULT constraint can also be used to insert system values, by using functions like GETDATE():-
  

CREATE TABLE tblEmployees
(
EmpID INT PRIMARY KEY,
EmpName VARCHAR(100),
Address varchar(200),
MobileNo bigint,
Email NVARCHAR(200) DEFAULT 'sa@gmail.com',
JoinDate date DEFAULT GETDATE()
)



How to Alter DEFAULT Constraint on TABLE in SQL:-
  

ALTER TABLE tblEmployees ALTER COLUMN Email SET DEFAULT 'sa@gmail.com'



How To DROP a DEFAULT Constraint in SQL:-
  

ALTER TABLE tblEmployees ALTER Email DROP DEFAULT