This one is also used to uniquely identify records or rows in another data table. It refers to the primary key in another table and acts as a link between two tables.
How to add Foreign Key in MySQL
CREATE TABLE office ( emp_ID int , emp_fName varchar(255) NOT NULL, emp_lName varchar(255) NOT NULL, Age int CHECK(Age <= 50) FOREIGN KEY (emp_lName) References office_two(emp_lName) );
This creates a foreign key constraint on emp_lName, referencing the office_two table.