Database Design Fundamentals

The real world is full of objects: * physical and tangible objects like houses, dogs, cars etc. * virtual objects like orders, requests, code libraries etc.

We call each class of objects entity.

There are relations between entities: * mother-child-relations: there might be many, one or no child, we call this a 1-to-many-relation and write 1:m * child-mother-relation: there is only one mother for each child, we call this a m-to-1-relation and write m:1 * woman-mother-relation: each woman might be a mother or not, we call this a 1-to-c-relation and write 1:c