Auto increment integer primary key data Transfer from one server to another

When i transferred data from one server to another i learned new thing.
we used integer primary key with auto increment in our database, instead of this if we would used guid, no need to take care of anything.

you can not transfer auto increment value because if transfer that value your primary key value changed in new database but doesn't change in your connected table.
so i found a new keyword out in mssql, we can use this keyword to used values stored in magic table means 'INSERTED','DELETED'

 update #customerOld set MerchantID = @NMerchantID  
 create table #customerPK (myNewPK INT,OldPK int,id int identity(1,1))  
 Insert into sai2.dbo.Customer  
 output INSERTED.CustomerID,0 INTO #customerPK   
 select MID,LoginID,Password,Pin,Email   
 from #customerOld As T  
 update #customerPK set OldPK = A.CustomerID from #customerPK AS T  
 inner join #customerOld AS A on A.ID = T.id