MySQL Foreign Key

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.