shrink database Ms SQL Server

usually used for reduce log file size at Ms. SQL

below steps script for reduce NORTHWIND database from 80GB become to 40GB:
(1) . backup the Log
BACKUP LOG NORTHWIND WITH NO_LOG
(2). cek logical name log
sp_helpdb NORTHWIND
(3). shrink the logical log become to 1024kb
DBCC SHRINKFILE (NORTHWIND_Log,1)