Red > Green > Refactor > Red

cycle is based on desire

normal form (NF)

  • 1NF
    • requiring existence of "the key"
  • 2NF
    • requiring the non-key attributes be dependent on "the whole key"
  • 3NF
    • requiring the non-key attributes be dependent on "nothing but the key"
header tag body
hello some hello world...
... ... ...
... ... ...

whole key = {header, tag}

Edgar F. Codd - Wikipedia, the free encyclopedia

database - Why need 2NF? - Stack Overflow