使用MySQL EXPLAIN优化查询

Question

I'm a bit of a db noob and have a nasty query that is taking over 30 seconds to run. I'm trying to learn a bit more about EXPLAIN and optimize the query but am at a loss. Here is the query:

SELECT 
    feed.*, users.username, smf_attachments.id_attach AS avatar, 
    games.name AS item_name, games.image, feed.item_id, u2.username AS follow_name
FROM feed
INNER JOIN following ON following.follow_id = feed.user_id AND following.user_id = 1
LEFT JOIN users ON users.id = feed.user_id
LEFT JOIN smf_members ON smf_members.member_name = users.username
LEFT JOIN smf_attachments ON smf_attachments.id_member = smf_members.id_member
LEFT JOIN games ON games.id = feed.item_id
LEFT JOIN users u2 ON u2.id = feed.item_id
ORDER BY feed.timestamp DESC
LIMIT 25

Explain results:

Answer 1

The result you will want to avoid in your execution plan (the output of an explain statement) is "full scan" (extra field of the explain output). In order to avoid it, you need to create the correct indexes on your tables.

If you have a table scan, it means the query engine read sequentially each row of the the table. Instead, with index access, the query engines accesses more directly the relevant data.

More explanation here: http://dev.mysql.com/doc/refman/5.0/en/using-explain.html