Final answer:
A foreign key is a reference to a primary key in another table, creating a relationship between the two tables. It should always be linked to a primary key of another table to maintain data consistency and integrity. Therefore, the statement that a foreign key should always be linked to a primary key of another table is true.
Step-by-step explanation:
A foreign key is a column or group of columns in a relational database table that is used to establish a link between the data in two tables. It is a reference to a primary key in another table, creating a relationship between the two tables. Therefore, the statement that a foreign key should always be linked to a primary key of another table is true.
For example, if we have two tables, 'Orders' and 'Customers', the 'CustomerID' column in the 'Orders' table can be a foreign key that references the 'CustomerID' primary key column in the 'Customers' table. This allows us to associate each order with a specific customer.
On the other hand, the statements that a foreign key can be linked to any foreign key and that a foreign key is not needed if the data type is different are not true. A foreign key must be linked to the primary key of another table to maintain referential integrity and ensure the data consistency and integrity in the database.