IT Specialist – Software Development Practice Test

In relational databases, a foreign key creates a link between two tables by referencing a key in another table. This is how relationships are modeled: a column (or set of columns) in one table points to the primary key (or another unique key) in a different table, establishing referential integrity. For example, an Orders table might have a CustomerID that references Customers.CustomerID. This ensures every order is associated with a valid customer, and you can join the tables to pull related data. A foreign key does not have to be unique within its table—many rows in the child table can reference the same parent row, enabling one-to-many relationships. It is different from a primary key, which uniquely identifies rows within its own table. And it’s not about permissions or storing large binary data; those correspond to other concepts.