左连接问题与哪里AND

将外部过滤器移动到JOIN条件.否则,过滤器将其更改为INNER JOIN

select Post.id, name, body,
(select count() from Votes where id=Post.id AND (type & 4)<> 0) as DV
from Post 
left join Votes as V on V.id=Post.id AND V.IPAddr <> 0 
where flag='1' AND DV<1
limit 1