Question

I am working on a twitter clone in PHP for school, and I have one major problem. I cannot find a way to implement a follower system. There is a table for users, and I want to add a field that holds the ids of all of the users that each user follows.

Should I separate the ids with commas and then split them apart in PHP? And then I need to select all of the tweets from the tweets table that were tweeted by any of the users followers. Is there an SQL command that I can use? Something similar to

SELECT *
FROM tweets 
WHERE author='$followeduser'"

but where $followeduser is multiple ids.

Answer 1

Have a USER_MASTER table like this

USER_ID (int)
USER_NAME(varchar(50))

Create a table called USER_FOLLOWERS like this

USER_FOLLOWER_ID // Auto increment-Primary Key for this record
USER_ID (int)  // foriegn key to UserId column in USER_MASTER table
FOLLOWER_ID (int)  // foriegn key to UserId column in USER_MASTER table

Store the UserId in the first column and store the UserId of the User who follows this user in the Follower_ID column.

So your data will look like this

USER_ID    USER_NAME
--------------------------------------
1           SCOTT
2           JARED
3           MARC
4           ERIC

USER_FOLLOWER_ID    USER_ID   FOLLOWER_ID
--------------------------------------
1                    1          2
2                    1          3
3                    1          4
4                    2          1

So this means , The User Scott has 3 followers, Jared, Marc and Eric. User JARED HAS one Follower, that is SCOTT

To get the list of Followers for a user(ex : Scott (ID=1)) , you can do a Join between these 2 tables

  SELECT U. USER_ID, U.USER_NAME From USER_MASTER U
  INNER JOIN USER_FOLLOWERS UF ON U.USER_ID=UF.FOLLOWER_ID
  WHERE UF.USER_ID=1  // 1 is the ID of SCott