Unable to open physical file operating system error 5: Access denied SQL Sever

Detach the attached database today, detach it and attach it again, no problem. But a. mdf file is copied to the other folder and an error is as follows:
The physical file "E:\db\homework.mdf" could not be opened. Operating system error 5: "5 (Access denied. )"。 (Microsoft SQL Server, error: 5120)

Asked a friend, friend said to find the. mdf file to change the security permissions of the file.

It took a while to understand that the original is to find. mdf file, right--Properties---security, select Current user, edit-and-Full control.

If this is the case, remember that the security permissions for the. log file are also

Unable to open physical file operating system error 5: Access denied SQL Sever