How do I write SQL query for the website traffic

I have a table record with the columns:

userId

ip

timestamp

userAgent

How do I write a query that will list the site traffic per month (measured in # of logins) from January 2017 through December 2017

Answer

You can use group by as follows:

select userId, date_trunc('month', timestamp) as Month_, count(*)
From your_table t
Where year(timestamp) = 2017
group by userId, date_trunc('month', timestamp) ;