add a Default Value Constraint

Question

I'm trying to add a Default Value Constraint but only if the Constraint doesn't already exist.

Comments

you can only overwrite the constraint but can not check the if it is null or not.

Answer 1

CREATE TABLE CUSTOMERS(
ID INT NOT NULL,
NAME VARCHAR (20) NOT NULL,
AGE INT NOT NULL,
ADDRESS CHAR (25) ,
SALARY DECIMAL (18, 2) DEFAULT 5000.00,
PRIMARY KEY (ID)
);