How to store multiple values in single column where use less memory?

Question

I have a table of users where 1 column stores user\'s \"roles\". We can assign multiple roles to particular user.

Then I want to store role IDs in

Answer 1

You can also use bitwise logic with MySQL. role_id must be in BASE 2 (0, 1, 2, 4, 8, 16, 32...)

role_id | label
--------+-----------------
      1 | Admin
      2 | User
      4 | Author

user_id | name  | role
--------+-----------------
      1 | John  | 1
      2 | Steve | 3
      3 | Jack  | 6

Bitwise logic allows you to select all user roles

SELECT * FROM users WHERE role & 1
-- returns all Admin users

SELECT * FROM users WHERE role & 5
-- returns all users who are admin or Author because 5 = 1 + 4

SELECT * FROM users WHERE role & 6
-- returns all users who are User or Author because 6 = 2 + 4