php - SQL Join multiple ids comma separated

Question

i have two tables, costs and users.

Costs table:

id | project | category | type | description | status | value | date_reg | date_edit | edited | id_user | name

Now i need, save id from users on id_user in costs table, how i do it? i save as 1|2|3 or 1,2,3 ? But i need join table users for get some infos, like name, email and others things.

Costs table: id_user 1|2|3|4 or 1,2,3,4 or anything.

User table: id | name | password | email | date_reg | level | photo

Because may have many users on the same project(table costs).

I want list users (from user table) infos by id_users on costs table. I am using codeigniter.

Answer 1

You need a new costs table to each cost:

Projects
-----------------
Project_id
Name

Users
--------------------
User_id
Username

Costs
----------------
Cost_id
Amount
Project_id
User_id

..

To find projects costs per project per user:

Select sum(c.Amount) as total_cost, count(*) as num_costs, p.Project_id,p.Name as project_name, u.user_id, u.Username
From costs c inner join project p on c.Project_id=c.Project_id
Inner join users u
On c.User_id=u.User_id
Group by p.Project_Id, u.user_id

For costs per user

Select sum(c.Amount) as total_cost, count(*) as num_costs, u.user_id, u.Username
From costs c 
Inner join users u
On c.User_id=u.User_id
Group by u.user_id