SQL Server does not have valid owner issues with this database

After you create a new database or attach a database, you want to add a relational table, resulting in the following error:

The database diagram support object cannot be installed because this database does not have a valid owner. To continue, first use the Files page of the Database Properties dialog box or the Alter
The authorization statement sets the database owner to a valid login, and then adds the database diagram support object.
The first way to change is not possible, and the owner of the file is also SA. Netizens have given a way to run the following command:
ALTER AUTHORIZATION on Database::mydbname to SA
To change the mydbname to the actual database name, you can set the owner to SA.

SQL Server does not have valid owner issues with this database