SQL DEFAULT Constraint

The DEFAULT constraint is used to provides a default value to a column.

The default value will be added to all new entered records If new records are not specified the value.

EXAMPLE: DEFAULT Constraint

Create a SQL new table 'EMPLOYEE' and adds Six columns like [EMPLOYEE_ID, NAME, EMAIL, ADDRESS, AGE, and SALARY]. Set the SALARY column is 10,000 by default, so if the INSERT INTO statement does not provide a value for SALARY column, then by default the SALARY column would be set to 10,000. For example the SQL DEFAULT query mentioned below:

CREATE TABLE EMPLOYEE (
   EMPLOYEE_ID INT   NOT NULL,
   NAME VARCHAR (100)   NOT NULL,
   EMAIL VARCHAR (100),
   ADDRESS CHAR (200),
   AGE INT    NOT NULL,
   SALARY DECIMAL (100, 3) DEFAULT 10000,
   PRIMARY KEY(EMPLOYEE_ID)
);

ALTER TABLE - DEFAULT Constraint

ALTER TABLE EMPLOYEE
MODIFY SALARY DEFAULT 10000;

DROP DEFAUL Constraint

To drop a DEFAUL constraint, use the following SQL commond:

ALTER TABLE EMPLOYEE
ALTER COLUMN SALARY DROP DEFAULT;