This Oracle tutorial explains how to enable a foreign key in Oracle with syntax and examples.
You may encounter a foreign key in Oracle that has been disabled. You can enable the foreign key using the ALTER TABLE statement.
The syntax for enabling a foreign key in Oracle/PLSQL is:
ALTER TABLE table_nameENABLE CONSTRAINT constraint_name;
If you had created a foreign key as follows:
CREATE TABLE supplier( supplier_id numeric(10) not null, supplier_name varchar2(50) not null, contact_name varchar2(50), CONSTRAINT supplier_pk PRIMARY KEY (supplier_id)); CREATE TABLE products( product_id numeric(10) not null, supplier_id numeric(10) not null, CONSTRAINT fk_supplier FOREIGN KEY (supplier_id) REFERENCES supplier(supplier_id));
In this example, we've created a primary key on the supplier table called supplier_pk. It consists of only one field - the supplier_id field. Then we've created a foreign key called fk_supplier on the products table that references the supplier table based on the supplier_id field.
If the foreign key had been disabled and we wanted to enable it, we could execute the following command:
ALTER TABLE productsENABLE CONSTRAINT fk_supplier;