I believe you mean "store multiple settings in one column".
If you're storing the set of permissions as an actual string of zeros and ones, as you've described, you can just use the substr() function to extract the relevant digit, and then perform whatever comparisons are necessary.
It'd be more efficient, however, to store the set of permissions as bits of an integer, using the the bitwise operators to set and check each permission. This is the usual way of storing a set of related boolean values. This is a little fidgety if you're not used to it.
In general, though, I use neither of these approaches. Instead, I have a table named "permissions", containing a definition of each permission the system needs to track. This might look something like this:
id|description
--+-----------
1 |Create new user
2 |Delete user
3 |View sales reports
4 |Send mass email
...and so on. Then, I have a second table, "user_permissions", that links user records to permissions. It contains one record for each permission that's enabled for each user, and might look something like this:
id|user_id|permission_id
--+-------+-------------
1 |43 |1
2 |43 |2
3 |52 |1
4 |52 |2
5 |52 |3
6 |52 |4
...and so on. Here, user 43 has permission to create and delete users; user 52 has all four permissions.
So, to determine whether user 43 has the "Delete user" permission, you'd do this:
SELECT 1 FROM user_permissions WHERE user_id = 43 AND permission_id = 2;
If this returns a row, the user has the permission. If it returns no rows, they don't.
I like this approach because it's easy to extend the system with additional permissions as needs arise, and it's easy to write admin screens for setting permissions.
Some variants of this basic technique are possible. You could use a string, instead of an integer, as the primary key for the permissions table - so your keys might be "CREATE_USER", "DELETE_USER", "VIEW_SALES", and "SEND_EMAIL", instead of 1, 2, 3, and 4. This makes your queries a little slower, but more readable.
