How to find the first day for the current month?

These functions are deployed in process/reports, SSIS ELTS to retrieve the information as per the dates given. The functions are given below with logical explanation:

First day of current month:

       Select DATEADD (mm, DATEDIFF(m,0,GETDATE()),0): Here we have calculated the difference between the months starting from 0 to present date and then summed up the difference in 0. This will give the first day of the ongoing month.
Last day of current month:
      SELECT cast (DATEADD(s,-1,DATEADD (mm, DATEDIFF(m,0,GETDATE())+1,0)) as date): beginning from innermost query (DATEDIFF(m,0,GETDATE())) will support you in calculating the difference between the months from 0 to current date. Then we will include a month which will turn it into next month. Then we must subtract 1 sec from it and this will provide the last second of the month. Then we will turn that into a date to extract the last day of the current month.
First day of next month:
      SELECT DATEADD(mm, DATEDIFF(m,0,GETDATE())+1,0) ): Here we have calculated the difference between the months from 0 to present date and then include 1 to the difference and 0. This will lead to returning the initial day of next month. 
Last day of next month:
       SELECT cast(DATEADD (s,-1, DATEADD(mm,DATEDIFF(m,0,GETDATE())+2,0)) as date)
First day of previous month:
      Select DATEADD(mm,DATEDIFF(m,0,GETDATE())-1.0)
Last day of previous month:
      SELECT cast(DATEADD(s,-1,DATEADD(mm,DATEDIFF(m,0,GETDATE()),0))as date)

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