What is the 2nd normal form?

Question

My unofficial view of them:

1NF : The table is partitioned so that no items appear more than once.

2NF :?

3NF : Values can only be determined by the primary key.

I cannot figure it out from excerpts that I found on the Internet or in my book. How can I distinguish between 1NF and 2NF?

+3

2 answers

Shaun · Answer 1 · 2012-04-11T20:58:08+0000

The relationship scheme is in 2NF if each non-prime attribute is fully functionally dependent on each key.

Carlos Gavidia · Answer 2 · 2012-04-11T21:14:43+0000

2NF , 1NF - non prime.

TOY_ID| STORE_ID| INVENTORY| STORE_ADDRESS

TOY_ID STORE_ID. non-prime INVENTORY, , TOY_ID STORE_ID . .

, STORE_ADDRESS, , STORE_ID (.. TOY_ID). 2NF, , 2NF, :

: TOY_ID| STORE_ID| INVENTORY

: STORE_ID| STORE_ADDRESS