It's best to use 2 tables here
1. User Types
You asked about the best way to code it, so I would change your table structure to below. Either way, your table columns will still work.
id:1
type: ceo
id: 2
type: programmer etc...
Then, in your users table, you have
id: 1
user: username
pass: password
user_auth: 1
It's best to use digits when possible.
Anyways, when you login, you would use a similar query as such:
$query = "select * from userstable WHERE username = '$user' AND password = '$pass'";
now, you have a specific user logged in. You can use the below to get more information about this user
while($row = mysql_fetch_assoc($query)){
$auth = $row['user_auth'];
}
$auth will display a number depending on their auth. You can now use if states to redirect etc...