Is it possible to have two identical values in a database table field related to another table via a foreign key?

Yes, a database table can have multiple identical values in a field that is linked to another table via a foreign key. A foreign key ensures referential integrity, meaning it guarantees that the value in this field exists in the related table.

However, a foreign key does not impose a uniqueness constraint on the values in its own table. This means that multiple records can refer to the same record in another table.

Example:

The Orders table has a customer_id field, which is a foreign key to the Customers table.

In the Orders table, there can be many orders with the same customer_id, as one customer can place multiple orders.

If you need the values to be unique, you should additionally use a UNIQUE or PRIMARY KEY constraint.