DirectAdmin determined the ownership of a database file by the file name, in the format username_dbname.
If the username of your database doesn't match your DirectAdmin database name, then you should rename the sql file before trying to import it. If you're trying to import a database you don't already have set up, then try creating it first, which will create a database name in the proper format.
Don't forget you may need to change your code to access the database.
If this isn't your problem or doesn't resolve it, then please post again in greater detail.
Jeff