解决 Discuz!X3.x “抱歉，该附件无法读取”的问题
报错信息：
抱歉，该附件无法读取
经排查，权限之类的完全正确，不要用哪些权限问题来糊弄人。
主要是这个表：pre_forum_attachment，丢掉了pre_forum_attachment_(0-9)中的附件数据 （aid,tid,pid, uid,tableid,downloads）。
解决办法：sql执行以下命令（有一个缺点，附件下载次数没有了。我这里模拟的是10次）。如果想完全的恢复，只能恢复备份数据重新执行。当然，我这边客户已经把备份数据手贱删除了。
再次郑重说明，删除数据一定要谨慎，数据无价，谨慎操作。
INSERT INTO pre_forum_attachment(aid,tid,pid, uid,tableid,downloads)SELECT aid,tid,pid, uid,1,'10' FROM pre_forum_attachment_0 d WHERE NOT EXISTS (select tid from pre_forum_attachment where pre_forum_attachment.aid = d.aid);
INSERT INTO pre_forum_attachment(aid,tid,pid, uid,tableid,downloads)SELECT aid,tid,pid, uid,1,'10' FROM pre_forum_attachment_1 d WHERE NOT EXISTS (select tid from pre_forum_attachment where pre_forum_attachment.aid = d.aid);
INSERT INTO pre_forum_attachment(aid,tid,pid, uid,tableid,downloads)SELECT aid,tid,pid, uid,2,'10' FROM pre_forum_attachment_2 d WHERE NOT EXISTS (select tid from pre_forum_attachment where pre_forum_attachment.aid = d.aid);
INSERT INTO pre_forum_attachment(aid,tid,pid, uid,tableid,downloads)SELECT aid,tid,pid, uid,3,'10' FROM pre_forum_attachment_3 d WHERE NOT EXISTS (select tid from pre_forum_attachment where pre_forum_attachment.aid = d.aid);
INSERT INTO pre_forum_attachment(aid,tid,pid, uid,tableid,downloads)SELECT aid,tid,pid, uid,4,'10' FROM pre_forum_attachment_4 d WHERE NOT EXISTS (select tid from pre_forum_attachment where pre_forum_attachment.aid = d.aid);
INSERT INTO pre_forum_attachment(aid,tid,pid, uid,tableid,downloads)SELECT aid,tid,pid, uid,5,'10' FROM pre_forum_attachment_5 d WHERE NOT EXISTS (select tid from pre_forum_attachment where pre_forum_attachment.aid = d.aid);
INSERT INTO pre_forum_attachment(aid,tid,pid, uid,tableid,downloads)SELECT aid,tid,pid, uid,6,'10' FROM pre_forum_attachment_6 d WHERE NOT EXISTS (select tid from pre_forum_attachment where pre_forum_attachment.aid = d.aid);
INSERT INTO pre_forum_attachment(aid,tid,pid, uid,tableid,downloads)SELECT aid,tid,pid, uid,7,'10' FROM pre_forum_attachment_7 d WHERE NOT EXISTS (select tid from pre_forum_attachment where pre_forum_attachment.aid = d.aid);
INSERT INTO pre_forum_attachment(aid,tid,pid, uid,tableid,downloads)SELECT aid,tid,pid, uid,8,'10' FROM pre_forum_attachment_8 d WHERE NOT EXISTS (select tid from pre_forum_attachment where pre_forum_attachment.aid = d.aid);
INSERT INTO pre_forum_attachment(aid,tid,pid, uid,tableid,downloads)SELECT aid,tid,pid, uid,9,'10' FROM pre_forum_attachment_9 d WHERE NOT EXISTS (select tid from pre_forum_attachment where pre_forum_attachment.aid = d.aid);