困难的 PHP/MySQL 代码

Question

I have 3 DB tables

1. users(userid etc)
2. friends(friendid,userid,friendsuserid)
3. updates(updateid, userid, update)

Basically I've coded a script that lets you update your profile with activity(like a status) and able to become friends with one another(using friends table, userid + friendsuserid = they friends)

However, when it comes to the home page displaying these updates, I can display mine(user logged in) totally fine, but the friends updates dont show.

I'm having problems with it as it seems a lot of querys need to happen, to select the user logged in the friends table and get their friends userid... then its another select query to select all the statuses with the user logged in id and the friends id. then another select query to select the information from all the users profile to display their name alongside the status.

At the moment, I can only think of looping the query and putting id's in an array, then putting the array into a select query for the friends updates and displaying them.. is there a better way? code is a mess lol and im getting confused with the amount of querys(basically 2 of each for the friends and for the user logged in) must be an easier way lol

Answer 1

I think you should look into JOINs and subqueries. You should make a "subquery" - select the user that is logged in then join on the friends table (to get all of the friends userIds) and then use that list to filter in updates table

basic joins explanation

subquery info

Answer 2

You can get updates of user and updates of user's friends by doing something similar to this.

SELECT u.*
FROM updates u INNER JOIN 
   (SELECT friendsuserid as userid FROM friends WHERE userid = [youruserid]
    UNION
    SELECT userid FROM friends WHERE friendsuserid = [youruserid]
   )f
ON u.userid = f.userid

Answer 3

Tin Tran,

yes all I can seem to get is this

select u.* from statusupdates u INNER JOIN (select friendsuserid from friends where userid = '2' UNION SELECT userid from friends where userid = '2')f on u.userid = f.friendsuserid;SELECT u.userid,u.email,u.name FROM users u INNER JOIN (SELECT friendsuserid FROM friends WHERE userid = '2' UNION SELECT userid FROM friends WHERE userid = '2')f ON u.userid = f.friendsuserid;

however am i right in thinking that is in fact two querys? That in a mysql command line(testing querys to see if they give me what i need before i code it in) gives me everything i need. However pretty sure mysql wont accept that in a php code as it's two querys. I've tried using inner join to add that users table to it but it doesn't seem to be correct

EDIT:

After messing around in command line i managed to get what i need

SELECT s.status,u.name,f.friendsuserid FROM statusupdates s JOIN users u ON s.userid=u.userid JOIN friends f ON u.userid=f.friendsuserid;

However, that only gives me my friends updates, not mine. I've tried putting a where in but it doesnt work.. I'm able to pull everything i need now, except my own updates and will it only display $_SESSION['userid'] statuses and their friends?