what is best format for statictics field in database

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MySQL

The main question is

What is best filed type that i can use in table “product_price” ?

Datetime

Timestamp

Or ...

And which format is best for it ?

I have 3 table

1 ) group -----> (group_id,group_name)

2 ) product --->(group_id,product_id,product_name)

3 ) product_price ----> (product_id,price_id,price_value,price_date)

Note : maybe in one day multi records saved . so time must save in date format ,too.

What is best filed(s) for Date in table “product_price” ?

I want to display any charts based on date from my database

(for example see http://www.kitco.com/charts/livegold.html[^])

I want that i can get different between first and last record(based on date field) from table “product_price” And then generate available date that user can see chart .

Example1)

Suppose different between first and last record is 35 days , in this case available chart is :

Today

Yesterday

Last week

Last month

Note : Last 3 month not available

Example2 )

Suppose different between first and last record is 253 days , in this case available chart is :

Today

Yesterday

Last week

Last month

Last 3 month

Last 6 month

Note : Last year not available

Example3 )

Suppose different between first and last record is 900 days , in this case available chart is :

Today

Yesterday

Last week

Last month

Last 3 month

Last 6 month

Last year

Last 2 year

Note : Last 3 year not available

And Finaly I say Again : The main question

What is best filed type that i can use in table “product_price” ?

Datetime

Timestamp

Or ...

And which format is best for it ?