如何在Amazon Redshift查询select上个季度/最近2个月的数据

Question

I know this is a simple question, but I just started to explore Redshift and couldn't google the answer yet.

In MSSQL server I use the following WHERE CLAUSE:

Last quarter:

WHERE DateTime>= DATEADD(qq,DATEDIFF(qq,0,GETDATE())-1,0) AND DateTime < DATEADD(qq,DATEDIFF(qq,0,GETDATE())-0,0) 

Last 2 months

WHERE DateTime>= DATEADD(mm,DATEDIFF(mm,0,GETDATE())-2,0) AND DateTime < DATEADD(mm,DATEDIFF(mm,0,GETDATE())-0,0)     

In the Redshift for the quarter I came out to:

WHERE DateTime>= dateadd(qtr,datediff(qtr,'1970-01-01',current_date)-1,'1970-01-01') AND 
DateTime < dateadd(qtr,datediff(qtr,'1970-01-01',current_date)-0,'1970-01-01')    

For the last 2 months it looks like:

WHERE DateTime>= dateadd(month,datediff(month,'1970-01-01',current_date)-2,'1970-01-01') AND 
DateTime < dateadd(month,datediff(month,'1970-01-01',current_date)-0,'1970-01-01') 

So, I have to use the unix epoch value instead of 0. Is there any better way to set this up?

Thank you very much!

Answer 1

In Redshift, I would use date_trunc() and interval arithmetics.

Last quarter:

where datetime >= date_trunc('quarter', current_date) - interval '1 quarter'
  and datetime <  date_trunc('quarter', current_date)

Last two months:

where datetime >= date_trunc('month', current_date) - interval '2 month'
  and datetime <  date_trunc('month', current_date)