Return just the last day of each month with SQL

Question

I have a table that contains multiple records for each day of the month, over a number of years. Can someone help me out in writing a query that will only return the last d

Answer 1

In SQL Server, this is how I usually get to the last day of the month relative to an arbitrary point in time:

select dateadd(day,-day(dateadd(month,1,current_timestamp)) , dateadd(month,1,current_timestamp) )

In a nutshell:

1. From your reference point-in-time,
2. Add 1 month,
3. Then, from the resulting value, subtract its day-of-the-month in days.

Voila! You've the the last day of the month containing your reference point in time.

Getting the 1st day of the month is simpler:

select dateadd(day,-(day(current_timestamp)-1),current_timestamp)

1. From your reference point-in-time,
2. subtract (in days), 1 less than the current day-of-the-month component.

Stripping off/normalizing the extraneous time component is left as an exercise for the reader.