In a database management system, a foreign key is a column or set of columns in a table that refers to the primary key of another table. A foreign key constraint maintains referential integrity by verifying that the values present in the foreign key column exist within the primary key column of the referenced table.
A foreign key cascade update is a referential action that updates the values in the foreign key column of a table when the values in the primary key column of the referenced table are updated. This allows you to update related data in multiple tables with a single update statement.