Is it possible to perform a bitwise group function?

Question

I have a field in a table which contains bitwise flags. Let\'s say for the sake of example there are three flags: 4 => read, 2 => write, 1 => execute a

Answer 1

You would need to know the possible permission components (1, 2 and 4) apriori (thus harder to maintain), but this is pretty simple and would work:

SELECT user_id,
       MAX(BITAND(permissions, 1)) +
       MAX(BITAND(permissions, 2)) +
       MAX(BITAND(permissions, 4)) all_perms
FROM permissions
GROUP BY user_id