Calculate the last day of the prior quarter

Question

What\'s the most efficient way to calculate the last day of the prior quarter?

Example: given the date 11/19/2008, I want to return 9/30/2008.

Platform is S

Answer 1

In amazon redshift:

Last day of the previous quarter:

select dateadd(day,-1,DATE_TRUNC('qtr', current_date)) from whatever

Last day of current quarter:

select dateadd(qtr,1,dateadd(day,-1,DATE_TRUNC('qtr', current_date))) from whatever