Designing relational databases

Выделение сущностей и их атрибутов

Атомизация сложных атрибутов на более простые.

Определение уникальных идентификаторов (первичных ключей)

Определение отношений между таблицами с помощью внешних ключей

Нормализация базы данных

Primary key value must be unique

Primary key cannot be NULL

Primary key values cannot be changed

The original key must be assigned a value when inserting a new entry

A foreign key may have a different name from its primary key

It ensures that rows in one table have corresponding rows in another

Unlike the primary key, they do not have to be unique. Most often they are not

Foreign keys may be null, although primary keys cannot

One to one (Один к одному)

One to many (Один к многим)

Many to many (Многие ко многим)

It should only have single(atomic) valued attributes/columns

Values stored in a column should be of the same domain

All the columns in a table should have unique names

And the order in which data did store, does not matter

It should be in the First Normal form

It should not have Partial Dependency

It is in the Second Normal form

It doesn’t have Transitive Dependency