DB Design - Assigning users to multiple sites with different roles
For the simplicity of maintaining it in the future (especially if it's not you) I would go with your first design. It contains a table with information on the user (login, name,etc), a table for the site (location, category) and then a table linking a person to a site (Steve is the account admin at Site 3) The second design would make things more complicated than they really needed to be