Hi everyone,

I have two MySQL tables in one database: 'users' and 'data'

When a user logs in to my website, I want to display their content from the 'data' table on their login page. The problem I'm running into is this: not all users should be able to view all data; instead, users should only be able to view data that belongs to them.

I think I'm over my head. Can anyone give any advice for how to do this?

Thanks!

Look for a tutorial on databases, you look like you really need one.
Like this one: http://www.sqlcourse.com/

In a relationnal database, what you are looking to do is the base of the system.
You told us that you had 2 tables, users and data.

I'm starting from the principle that a user that is registered in your system have an id.
I'm considering that those users can save datas in your database, and that those datas will have something that will link them to a user.

The step to put everyting together are called "joins". You will tell the database engine that you want to join the inforamtions from the 2 (can be way more than that) tables to display only some that correpond to the filters you will define.

Supposing that your tables look a bit like that:

users:
  id integer
  username varchar

datas:
  id iteger
  user integer
  data1 varchar
  data2 varchar

In this case, the link between the datas and the users would be the field datas.user
Being an integer, it would mean that the value in that field would match the users.id field, telling that the row X in table datas have been created by the user n° Y

As you already know, you can do 2 select, and parse them in php.
But you can join the tables on that common field too, like this

select users.username, datas.data1, datas,data2
from users
  inner join datas on datas.user=users.id

But I urgently recommand you to follow the tutorial I've gived you, you relly need to strenghten your sql knowledges if you are to be working with databases.
from

Wow, thanks for that overview, that was great!

And I'm taking a look at the link you provided now.

You should have a read up on sql JOINs. (http://en.wikipedia.org/wiki/JOIN) basically it means associating a row in one table to another row in a different table, based on a join criteria.

For example,
If your table structures were as follows:

User( userID, username, password, name )
Data( dataID, userID, content )

Your query would look something like this

//Explicit inner join
SELECT * FROM Users u INNER JOIN Data d ON u.userID = d.userID AND u.userID= X

//implicit inner join
SELECT * FROM Users u, Data d WHERE u.userID = d.userID AND u.userID = X

Hope this helps!

Sorry, i wrote that last night and forgot to press submit! hope its all going well!