It is possible that two people or companies, or products, can have exactly the same name. It is also possible that, even ignoring error and variation, people, places and things have more than one name:

The relationship between a name and that which it names is quite naturally a true "many-to-many relationship".

It is not surprising that indexing these "many to many" relations requires careful design in the majority of today’s relational databases, whose constructs are limited (with some good reason) to architectures based on "one to many" relations.

The design of a record or row that contains two fields, one for "name" and one for "maiden name", or "registered name" and "trading name", may make logical business sense, but it is not good for indexing.

When we are searching for a person name, company name or address we do not know which "role" it plays. We do not know if it is a birth name, married name or maiden name, we do not know if it is a current or prior address. In order to address this problem effectively, it is necessary to have several index entries pointing to the same record. The alternative of declaring a separate index on each field or attribute is totally prohibitive from a performance point of view.

Solving this "many to many" characteristic of names leads to an additional table or file in most databases. It therefore requires that this table is maintained in sync with the main business tables.