Final answer:
A. foreign keys
Foreign keys are used to implement 1:1 and 1:M relationships in an REA diagram in a relational database.
Step-by-step explanation:
In implementing an REA diagram in a relational database, the foreign keys are used to implement 1:1 and 1:M relationships. Foreign keys are columns in a table that refer to the primary key column of another table. They establish a link between tables and help maintain data integrity.
For example, if we have a table for customers and a table for orders, the foreign key in the orders table would refer to the primary key in the customers table, enabling the connection between a customer and their orders.
In implementing an REA (Resources, Events, Agents) diagram in a relational database, the foreign keys are used to implement 1:1 and 1:M (one-to-one and one-to-many) relationships.
A foreign key is a field in a relational table that matches the primary key column of another table. It can uniquely identify a record in the relational database table and link the records in two tables together, allowing the database management system to maintain referential integrity.
For example, in a one-to-many relationship between 'Customers' and 'Orders', each order record would include the customer's primary key as a foreign key in its table to indicate which customer placed the order.