How to recover a database backup to an existing database that is already in use _mssql

Use master--(cant sit in the database whilst its being restored!)
Go

ALTER DATABASE MyDatabase SET single_user with ROLLBACK IMMEDIATE
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--Restore Full Backup
RESTORE DATABASE MyDatabase
From DISK = X:\MSSQL\BACKUP\MyBackupFilename_Full.BAK
With
REPLACE,
NORECOVERY,--use if more t/logs to recover
--RECOVERY,--use if NO more t/logs to recover
STATS = ten,--show progress (every 10%)
Move Mydatabase_data to X:\MSSQL\DATA\MyDatabase.mdf,
Move Mydatabase_log to X:\MSSQL\DATA\MyDatabase.ldf
Go

--Optional Restore differential Backup
RESTORE DATABASE MyDatabase
From DISK = X:\MSSQL\BACKUP\MyDatabase_Diff.BAK
With
--RECOVERY--use if NO more file to recover
NORECOVERY--use if there are t/logs to recover
Go

--Optional restore Transaction Log Backup
RESTORE DATABASE MyDatabase
From DISK = X:\MSSQL\BACKUP\MyDatabase_yyyymmdd_hhmm_Trans.BAK
With
--RECOVERY--use if NO more t/logs to recover
NORECOVERY--use if more t/logs to recover
Go

--Set The database ready for use (after all backups have been restored)
RESTORE DATABASE MyDatabase RECOVERY
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--Rename logical names (only needed if restoring to a backup for a different database):
ALTER DATABASE MyDatabase
MODIFY FILE (NAME = origdatabase_data, NEWNAME = mydatabase_data)
Go
ALTER DATABASE MyDatabase
MODIFY FILE (NAME = origdatabase_log, NEWNAME = Mydatabase_log)
Go