带有条件的左连接怎么写？
select top 100 percent a.announce_id,a.topic_id,a.parent_id,b.lastpost
from bbs_announce a where status=1 and is_black=0
left join bbs_topic b
on a.topic_id=b.topic_id
问题点数：50、回复次数：4Top
1 楼631799（杭州工人）回复于 2004-09-03 19:44:31 得分 0
自已搞定。
select top 100 percent a.announce_id,a.topic_id,a.parent_id,b.lastpost
from bbs_announce a
left join bbs_topic b
on a.topic_id=b.topic_id and status=1 and is_black=0Top
2 楼pengda1i（冒牌大力 V0.4）回复于 2004-09-03 19:50:53 得分 0
select top 100 percent a.announce_id,a.topic_id,a.parent_id,b.lastpost
from bbs_announce a
left join bbs_topic b
on a.topic_id=b.topic_id
where status=1 and is_black=0
Top
3 楼pengda1i（冒牌大力 V0.4）回复于 2004-09-03 19:51:07 得分 50
select a.announce_id,a.topic_id,a.parent_id,b.lastpost
from bbs_announce a
left join bbs_topic b
on a.topic_id=b.topic_id
where status=1 and is_black=0
Top
4 楼631799（杭州工人）回复于 2004-09-03 19:51:25 得分 0
不行没用，请指点Top
