The first normal form (or 1NF) requires that the values in each column of a table are atomic. By atomic we mean that there are no sets of values within a column.
From a performance point of view, an integer used as a surrogate primary key can often provide better performance in a join than a composite primary key across several columns.
this disproves another article ive recently read
One to (Zero or) One
One to (Zero or) Many
Many to Many
many-to-many relationship: A book can have more than one author, and an author can write more than one book.
one-to-many relationship exists between the Book table and the Publisher table. A given book has only one publisher (for our purposes), and a publisher will publish many books.
Where the First Normal Form deals with atomicity of data, the Second Normal Form (or 2NF) deals with relationships between composite key columns and non-key columns.
An INNER JOIN query returns one row for each pair or matching rows in the tables being joined.