能否上下 join?

x^^x

（SELECT f.friend_with fid, m.name, m.bday_year, x.gender, x.avatar
FROM friends f, member m, extra x
WHERE m.id=x.id AND f.friend_with=m.id AND f.member_id=$id AND approval=1) t1

（SELECT f.member_id fid, m.name, m.bday_year, x.gender, x.avatar
FROM friends f, member m, extra x
WHERE m.id=x.id AND f.member_id=m.id AND f.friend_with=$id AND approval=1)

t1 与 t2 的结构是一样的。 请问要如何只执行一次query, 将t1和t2 join(不是横向式， merge？) 起来？
是否类似SELECT * FROM t1, t2 ???

x^^x

谢谢你的回复和帮忙……