MySQL and Bit Bashing - mysql

Question

I'm using Bit bashing on SQL for user rights, like UNIX rights :
1 - 001 - Execute
2 - 010 - Write
4 - 100 - Read
So if I have right 6 ( 2+4 or 110) I can write AND read but I can't execute. On my case i have many more rights, so my users can have the value "128" for rights.
How can I do a query and ask all used with a right (like 2 for UNIX example)
SELECT * from user WHERE user_right ?? '2'
The users rights must be 2 (010), 3 (011), 6 (110) or 7 (111) ?!
Thank you all and sorry for my English :/

Answer 1

128 would mean there were 7 total user rights:
1 1 1 1 1 1 1 = 0177 = 0x7F = 127
MySQL already has an abstraction for this, known as the SET type, which essentially maps your named/visible value for the right to a binary value. So if you had a set column user_right:
('Execute', 'Write', 'Read')
They would actually be stored on the server backend as:
(1, 2, 4)
This allows for normal queries like:
SELECT * FROM user WHERE user_right LIKE '%Write%';
or using FIND_IN_SET:
SELECT * FROM user WHERE FIND_IN_SET('Write',user_right) > 0;
or direct bitset operations:
SELECT * from user WHERE user_right & 2;
to name a few. If you add an ORDER BY user_right to your select queries, it returns them in their numerical (not alphabetical) order, but otherwise you can quickly determine the values of a user with:
SELECT user_name, user_right FROM user;
and seeing that the returned value is:
'some user' | Read,Write
while still having the benefits of bitwise operations for very fast filtering, such as:
SELECT user_name, user_right FROM user WHERE user_right & ~1;
to return all users with read and write permissions that do not have execute rights.