Limit query results to two rows per group

Question

I have a query to list all posts:

SELECT *, DATE(FROM_UNIXTIME(`timestamp`)) `date` 
FROM `posts`
ORDER BY `date` DESC

The query list all rows,

Answer 1

This might work, though I couldn't say much about it's performance...

SELECT DATE(FROM_UNIXTIME(MyTimestamp)) AS ForDate, *
FROM   MyPostsTable
WHERE  2 >=
(
    SELECT COUNT(*)
    FROM   MyPostsTable AS lookup
    WHERE  DATE(FROM_UNIXTIME(lookup.MyTimestamp)) = DATE(FROM_UNIXTIME(MyPostsTable.MyTimestamp))
    AND    lookup.MyTimeStamp >= MyPostsTable.MyTimestamp
)