Question

Still wrapping my head around SQL and PHP, but hope someone can help with this:

I have the following tables:

1.

user table
- id
- name
- email

2.

user_group table
- user_id
- group_id

3.

group table
- id
- group_name

There is a many-to-many relationship between the user table and the group table. Now what I am trying to do build a browse users page which lists all the users in the system along with the groups that they belong to, so the page would look something like this:

Name: John Doe
Groups: football, tennis, swimming

Name: Jane Doe
Groups: hockey, basketball

Name: Jim Doe
Groups: hockey, football, rugby

etc. etc.

To accomplish this, I have the following SQL:

SELECT `user`.name, `group`.name 
FROM `user`, `user_group`, `group` 
WHERE `user`.id = `user_group`.user_id 
  AND `group`.id = `user_group`.group_id 
GROUP BY `user`.id, `group`.id

which returns results as follows:

1. John Doe | football
2. John Doe | tennis
3. John Doe | swimming
4. Jane Doe | hockey
5. Jane Doe | basketball
etc. etc.

As you can see, the results returned need to be manipulated in order to produce the comma separated groups shown earlier, as .

Is there a simple way to get the page to display the groups so that they are in a comma separated list for each user in MySQL? Or do I have to write PHP code to loop through the results looking for duplicate IDs and generating the comma-separated lists of groups on the page? Or am I doing something completely wrong in my approach?

Many thanks.

Answer 1

There are a few options (in order of my personal preference).

1. Don’t group by user id, and iterate trough your result and create an multi dimensional array using the user id as a key.
2. Use GROUP_CONCAT, which isn’t pretty.
3. Use separate queries for selecting all groups + users, and iterate to create an multi dimensional array.