Redshift gives us an easy way to get the date of the last day of a month. We no longer need to do date based calculations or tricks with date parsing. All we need is the last_day function.
The last_day function requires one parameter: a date or a timestamp. As the return value we will get the last day of the same month as the one given in the parameter. For example, if I pass 2020-12-18 to the function, I will get 2020-12-31:
select last_day(to_date('2020-12-18','YYYY-MM-DD'))
