怎么在mysql中 删除重复数据只保留一条

应该是由于 bt_ask_to_cate_backup 在 where 条件里出现了吧，可以copy出一个新表，然后用新表做查询条件 ,下边的代码没测试过。注意备份你的数据

create table bt_ask_to_cate_backup_temp select * from bt_ask_to_cate_backup;
delete from bt_ask_to_cate_backup 
where (ask_id, cate) 
    in (SELECT ask_id, cate 
        FROM bt_ask_to_cate_backup_temp 
        group by ask_id,cate 
        having count(*) > 1
    ) 
and id 
    not in (SELECT min(id) 
            FROM bt_ask_to_cate_backup_temp 
            group by ask_id,cate 
            having count(*) > 1
        )