How to SET DATEFIRST equal to Sunday in Amazon Redshift

Question

2016-01-01 is the week 1 of 2016, but also is the week 53 of 2015.

When I run SELECT DATE_PART(w, \'2016-01-01\') it returns 53, but when I run

Answer 1

Create a custom function with this case statement or use it in your SQL statements:

case when DATE_PART('W', dt)>=51 and EXTRACT(DOY FROM dt) < 8 then 1 else DATE_PART('W', dt)+1 end week_no

It will start counting weeks on Jan 1st.

http://sqlfiddle.com/#!15/ccb90/9