Assigning group membership to users from Mysql database using PHP

Question

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Users table

Id username  firstname  lastname
1  pmartin   Paul   Martin
2  pnorton   Peter  Norton
3  ladams    Lee    Adams

Group_membership table

Id  Group
1   Administrators
2   Developers
3   Technicians

Help is needed. I have registered users in Mysql database users table. These users can logon to the system with their username. From a different web page, I want to assign group membership to each registered users by using PHP and MySQL. I do not know how I can achieve this.

Exemple;

Users        group_membership
pmartin  ->  Administrators, Developers
pnorton  ->  Technicians
ladams   ->  Developers, Technicians

Answer 1

Since, there is a many to many relationship here, create a new table to map user ids with membership id

user_membership
----------------
id              - PK
user_id         - foreign key referencing Users.id
membership_id   - foreign key referencing Group_membership.id

and use joins later to get the relevant details.

Do not be tempted to store multiple values in one row as CSV. Normalization is your friend.