How to add a foreign key in PL/SQL table?

 

create table tbl_product(
    product_id number(10) NOT NULL,
    product_title varchar2(100) NOT NULL,
    product_description varchar2(255) NOT NULL,
    category_id number(10) NOT NULL
);

alter table tbl_product ADD CONSTRAINT pk_product_id PRIMARY KEY(product_id);

alter table tbl_product ADD CONSTRAINT fk_category_id FOREIGN KEY(category_id) REFERENCES tbl_category(category_id);