Here are some SQL queries that I find very useful when writing stored procedures. Using these queries, you can easily find the first date and last date of the current month, previous month or next month.

Current Date without Time:

SELECT DATEADD(day, DATEDIFF(day, 0, GETDATE()), 0)

First Date of Current Month:

SELECT DATEADD(mm, DATEDIFF(mm, 0, GETDATE()), 0)

First Date of Previous Month:

SELECT DATEADD(mm, DATEDIFF(mm, 0, GETDATE()) - 1, 0)

First Date of Next Month:

SELECT DATEADD(mm, DATEDIFF(mm, 0, GETDATE()) + 1, 0)

Last Date of Current Month:

SELECT DATEADD(s,-1,DATEADD(mm, DATEDIFF(m,0,GETDATE())+1,0))

Last Date of Previous Month:

SELECT DATEADD(s,-1,DATEADD(mm, DATEDIFF(m,0,GETDATE()),0))

Last Date of Next Month:

SELECT DATEADD(s,-1,DATEADD(mm, DATEDIFF(m,0,GETDATE())+2,0))

Convert Date to YYYYMMDD

SELECT CONVERT(VARCHAR(10), Now(), 112)