存储数据时mysql中表结构的首选方法

Question

Hey im building app which takes use of mysql. I am storing user data in users table and groups data in groups table. Predicted user's in total is little over 100

I was wondering is there any downsides or which is preferred method of constructing such structure like described below. I am using php to manage mysql data.

Now I have two tables:

Users
-----

id, firstname, lastname, in_groups
----------------------------------

1, Jake, New house, [1]

35, Gavin, McInnes, [1, 32, 41]  

Groups
------

id, group_name, group_password, total
--------------------------------------------

1, Destroyers, password, 1

32, Gamers, password, 41

41, Media, password, 22

Is this good method or should I divide this into more tables like

in_group
--------

id, user_id, group_id
---------------------
1, 1, 1

2, 35, 1

3, 35, 32

4, 35, 41

Answer 1

Definitely better to use the separate in_group table. That will make it equally easy to select all the "users in a group" (currently hard) as "groups for a user" (currently easy), plus even for the easy "groups for a user" query, right now you need to parse that out separately and by using a separate table you just read the rows of the results.

There is another advantage if you have multiple updates going on at the same time. Right now any update would replace the entire set of groups for a user. By separating the tables, you could have the ability to add or delete a group from a user without having any effect on the other groups for the user. There are other ways around that potential problem, but a separate table makes it very simple to handle.