Question

I need some help designing a friends system

The mysql table:
friends_ list
– auto_ id
– friend_ id
– user_ id
– approved_ status

Option 1 = Everytime a user adds a user there is 2 entries added to the DB, we then can get there friends like this

SELECT user_id FROM `friends_list` WHERE friend_id='$userId' and approved_status='yes'

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Option 2 = We add 1 entry for every friend added and then get the friend list like this

SELECT friend_id AS FriendId FROM `friends_list` WHERE user_id='$userId' and approved_status='yes'
UNION
SELECT user_id as FriendId FROM `friends_list` WHERE friend_id='$userId' and approved_status='yes'

Of the 2 methods above for having friends on a site like myspace, facebook, all the other sites do, which of the 2 methods above would be best performance?

The 1st method doubles the ammount of rows, example a site with 2 million friend rows would only be 1 million rows the second method.

However does the union method mean there is 2 queries being made, so 2 queries on a million row table instead of 1?

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UPDATE

I just ran some test on 60,000 friends and here are the results, and yes the tables are indexed.

Option 1 with 2 entries per friend;
.0007 seconds

Option 2 with 1 entry per friend using UNION to select
.3100 seconds

Answer 1

Option 1.

Do as much work as possible on adding a friend. Adding someone is very rare compare to selecting all friends. Something probably done every time you render a page (on a social site).