Help On Postgresql

Dear Friends

I am Jaydip Dewanji working as a Sr. Programmer for Ontrack Systems Ltd.

I have some questions regarding Postgresql which are listed below:

a) How do I retrieve the Year,Month,Day,Hr,Minute or Second value from a Date/DateTime variable.

For Example : i> In Oracle to_char(dt,'yyyy') - for extracting the year value from a date variable dt
ii> In SqlServer datepart(hh,dt) - for extracting the Hour value from a date variable dt

b) Can I create an identity column in Postgresql the value of which column will start from 1 say and keep
on incrementing by 1 OR how can I serve my purpose in any other way.

Please do let me know if any one of you have any solution.

Regards

Jaydip