Get data for previous month in postgresql

Question

SELECT * FROM Conference WHERE date_start ---don't know how to proceed--- 

How to check if date_start has been in the previous month ? Thanks you.

Answer 1

Subtract one month from the current month, then "truncate" that to the beginning of that date. As you don't want to include rows from "this" month, you also need to add a condition for that

SELECT * FROM Conference  WHERE date_start >= date_trunc('month', current_date - interval '1' month)   and date_start < date_trunc('month', current_date) 

date_trunc('month', current_date - interval '1' month) will return the 1st day of the previous month and date_trunc('month', current_date) will return the first day of "this" month.