Which of the following describes a One-to-Many relationship in databases?

• A. Multiple entries in one table reference a single entry in another
• B. One entry in a table can link to multiple entries in the same table
• C. Each entry must be unique across all tables
• D. Multiple tables reference each other

Answer: (A)

In a One-to-Many relationship in databases, multiple entries in one table can reference a single entry in another table. This means that for one record in the parent table, there can be many related records in the child table. For instance, if you have a table of "Customers" and a table of "Orders," each customer can place multiple orders, but each specific order is linked to only one customer. This relationship is fundamental in relational database design because it allows for organized storage and retrieval of related data without redundancy.

In contrast, the other options describe different scenarios that do not accurately represent a One-to-Many relationship. One entry linking to multiple entries within the same table describes a recursive relationship, while uniqueness across all tables pertains more to the concept of primary keys and integrity constraints rather than the relational structure itself. The mention of multiple tables referencing each other suggests a many-to-many relationship, which is distinct from One-to-Many. Understanding these distinctions is crucial for effective database design and management.