Oracle Constraints.(you might be knowing...just for refresh)

Oracle Constraints…

 

 

We can add, drop, enable and disable constraints in the Oracle…

 

 

Syntax for adding a constraint..

 

ALTER TABLE table

ADD [CONSTRAINT constraint] type (column);

 

 

e.g.

 

ALTER TABLE EMPLOYEE

ADD CONSTRAINT emp_manager_fk

FOREIGN KEY(manager_id) REFERENCES employee(employee_id)

 

 

 

Syntax for dropping a constraint…

 

 

ALTER TABLE EMPLOYEE

DROP CONSTRAINT emp_manager_fk

 

 

 

 

Syntax for enabling and disabling a constraint…

 

ALTER TABLE EMPLOYEE

DISABLE CONSTRAINT emp_manager_fk

 

ALTER TABLE EMPLOYEE

ENABLE  CONSTRAINT emp_manager_fk