In a 1-1 relationship, how must the extension entity Identifier be assigned?

In a one-to-one relationship within a database context, it is essential for the identifiers to be handled correctly to ensure that each record in the primary entity has a corresponding record in the extension entity. When an extension entity is created, particularly in a one-to-one relationship, it is critical that the identifier in the extension entity matches the identifier in the primary entity to maintain this relationship integrity.

Assigning the identifier programmatically ensures that the extension entity's identifier is directly correlated to the primary entity's identifier. This approach allows for a systematic way to enforce the linkage, ensuring that every record in the primary table has a corresponding record in the extension table without duplication or inconsistency.

Using an auto-number or a text field for the extension entity's identifier could lead to potential mismatches, as those methods do not inherently guarantee that each identifier corresponds directly to the primary entity's identifier. In scenarios where uniqueness and referential integrity are crucial, programmatically assigning the identifier is the safest and most reliable method.