How to convert a table to second normal form?

Question

Database

I have a relation in 1 normal form: employee #, employee name, employee's date of birth, employee's child name, child's date of birth. Primary key: employee number, child's name. How can we bring this relation to 2 normal form?

Answer 1

Since the primary key is composite and consists of the employee number, we decompose the child's name into 2 relations:
2 normal form

Answer 2

The 2NF requirement is that non-key attributes do not depend on part of the composite key. The date of birth of the child depends only on his name. Those. only from the "Employee, child's name" part of the key. Therefore, in order to reduce to 2NF, it is necessary to decompose the relation by making a separate table "Child's name, date of birth of the child".
PS Replacing your composite primary key with id, by the way, also formally leads to 2NF. But it is.