mysql: please help me get rid of nested clauses - mysql

Question

I have written the following query (the repeated parts put together from string constants) that tries to do the following in a shared calendar app.
search status_relation for all users with status not equal to 0 at current date+time
search default_status_relation for all users with status not equal to 0 at current weekday+time. This gives default weekly statuses when nothing is available in status_relation.
full outer join the two
then join on usernames from userid
this then gets processed by php which will display either the status (or default status, if status doesn't exist) of all users on that day who have status!=0.
the php needs to know whether it was returned a status or default status
Currently the query works (with a UNION to simulate an outer join). However, I would like to optimize it - I understand removing the subqueries might help. How can that be done?
SELECT q.*,
users.username,
users.userid AS uid
FROM (SELECT *
FROM ((SELECT sr.status AS srstatus,
dsr.status AS dsrstatus,
sr.userid AS sruserid,
dsr.userid AS dsruserid
FROM (SELECT *
FROM status_relation
WHERE DATE = '2012-03-19'
AND TIME = '0'
) sr
LEFT JOIN
(SELECT *
FROM default_status_relation
WHERE weekday = '0'
AND TIME = '0')
) dsr
ON sr.userid = dsr.userid)
UNION
(SELECT sr.status AS srstatus,
dsr.status AS dsrstatus,
sr.userid AS sruserid,
dsr.userid AS dsruserid
FROM (SELECT *
FROM status_relation
WHERE DATE = '2012-03-19'
AND TIME = '0') sr
RIGHT JOIN (SELECT *
FROM default_status_relation
WHERE weekday = '0'
AND TIME = '0') dsr
ON sr.userid = dsr.userid)
) myjoin
WHERE ( ( sruserid IS NOT NULL
AND srstatus != '0' )
OR ( sruserid IS NULL
AND dsrstatus != '0' ) )) q
LEFT JOIN users
ON ( q.sruserid = users.userid
OR q.dsruserid = users.userid )

Answer 1

You should be able to replace this part :
(SELECT sr.status AS srstatus,
dsr.status AS dsrstatus,
sr.userid AS sruserid,
dsr.userid AS dsruserid
FROM (SELECT *
FROM status_relation
WHERE DATE = '2012-03-19'
AND TIME = '0'
) sr
LEFT JOIN
(SELECT *
FROM default_status_relation
WHERE weekday = '0'
AND TIME = '0')
) dsr
ON sr.userid = dsr.userid)
by
SELECT sr.status AS srstatus,
dsr.status AS dsrstatus,
sr.userid AS sruserid,
dsr.userid AS dsruserid
FROM status_relation sr
left join default_status_relation dsr
ON sr.userid = dsr.userid and
sr.date = '2012-03-19' and
sr.time = TIME = '0' and
dsr.weekday = 0 and
dsr.time = 0;
You can do the same on the UNION