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Re: First,Second and Third Normal Form

ambrose1 — Sun, 05 Jul 2009 06:56:35 GMT

Thank u ramireddyindia,

I understand the concept...........Thanks a Lot for spending time with my questions.....................

Re: First,Second and Third Normal Form

ramireddyindia — Sat, 04 Jul 2009 16:47:31 GMT

We can tell that a table is in second normal form if it saitisfies the following.

i) It should be in first normal form.

ii) When the Table has only single column primary key, then it means automatically in second normal form. otherwise if the table has a composite primary key, then the other column should depends on all the columns of that composite key.

Eg:

OrderItems Table (ORderId,ItemId,ItemDescription,ItemQty,ItemPrice)

Now this table represents the Items ordered in that order.

that means the primary key is both OrderId and ItemId

Now check the remaining columns,

ItemDescription : Description of the Item, means it depends only on Items table. so this column depends only on ItemId column. so this column is not allowed.

ItemQty : The Quantity of the Item ordered in That Order. this column depends on both the columns. so this column is ok.

ItemPrice : the Price of the Item. again it depends only on ItemId column. so this column is not allowed.

so ,we will split it into 2 parts

OrderITems (OrderId,ITemId,ItemQuantity)

Items(ItemId,ItemDescription,ItemPrice)

Re: First,Second and Third Normal Form

ambrose1 — Sat, 04 Jul 2009 15:50:50 GMT

Thank u ramireddyindia,

I understand the Third Formal Form,Your example is so good.Can u give some Example for second normal form,It will so helpful for me....I can use it in the future................

Re: First,Second and Third Normal Form

ramireddyindia — Sat, 04 Jul 2009 14:44:34 GMT

In 3NF, Every Non_Key Field must depends on only keyfield. it should not depends on another Non_key Field.

Eg:

Orders Table:

OrderId CustomerName CustomerPhoneNo

1 x 123

2 y 345

3 x 123

In above table OrderId is the only KeyField of the table, Customer Name and CustomerPhoneNo are the non-key Fields. and customer phone number depends on Customer Name. It should depends on only keyfields. but its currently depends on non-key field "customername". so the above table is not in third normal form.

so we will make it as 2 tables.

Orders Table : ORderId,CustomerId

Customers Table: CustomerId,CustomerName,CustomerPhoneNo

Re: First,Second and Third Normal Form

ambrose1 — Sat, 04 Jul 2009 14:03:29 GMT

Thank u akhhttar,Anits,ramireddyindia,AvanthaSiriwardana

I came to understand First and Second Normal form,But it would be helpful for me,if u explain the third normal form with some simple examples here....so that I can understand it very clearly................

Re: First,Second and Third Normal Form

AvanthaSiriwardana — Sat, 04 Jul 2009 06:49:14 GMT

http://www.databasejournal.com/sqletc/article.php/1428511/Database-Normalization.htm

Re: First,Second and Third Normal Form

ramireddyindia — Sat, 04 Jul 2009 06:43:51 GMT

http://www.phlonx.com/resources/nf3/

Re: First,Second and Third Normal Form

Anits — Sat, 04 Jul 2009 06:42:05 GMT

Plz go thr this link.

http://www.bkent.net/Doc/simple5.htm

Re: First,Second and Third Normal Form

akhhttar — Sat, 04 Jul 2009 06:41:04 GMT

Hi,

Please see following articles,

For high level overview of notmalizations and theri forms: http://databases.about.com/od/specificproducts/a/normalization.htm

For Detail look with examples: http://www.phlonx.com/resources/nf3/

Hope these articles will help you to understand the concepts of database normalizations and their different forms.

Thank You

Muhammad Akhtar Shiekh

First,Second and Third Normal Form

ambrose1 — Sat, 04 Jul 2009 03:26:18 GMT

Hello Friends,

Can u Explain First,Second and Third Normal form in a Easy way with simple Examples.

Thanks in Advance