Why people are referring one to one mapping in SQL while there is Many to one relation?

The one-to-many and one-to-one relation are implemented in a slightly different way.


Object (objectId) ObjectCharacteristics(charId,objectId)


The order of the table is not important:

Husband (husbandId) Wife(wifeId,husbandId) + unique constraint on husbandId

N.B. One-to-many relation is also a one-to-one relation in the order way. The ObjectCharacteristics has one and only one object.

But you are right the relationship is a concept that does not depend upon the specific data in your database but only on the structure of it.