Mysql automatic backup problem

@echo off
C:\MySQL\bin\mysqladmin -u root --password=123456 shutdown
C:\MySQL\bin\mysqldump --opt -u root --password=123456 bbs > D:\db_backup\bbs.sql
C:\MySQL\bin\mysqld-nt

Save the above code backup_db.bat
then use the Windows "Scheduled Tasks" timed to the script execution. (Example: 5:00 daily execution back_db.bat)

After running the above script, bbs.sql file is generated, but the file is opened with Ediplus very slow speed, sql backup file with a tool to open quickly, which is why it?