一 查询数据库所有数据（包含不重复数据）
'select MIN(b.id) as min_id from stang_big_fagui as b WHERE b.wangzhan="裁判文书网" group by b.title,b.author,b.pubtime;'
二 查询数据库所有重复数据（不包含单条数据）
select MIN(id) from stang_big_fagui WHERE b.wangzhan="裁判文书网" group by title, author, pubtime having count(*)>1;
三 查询数据库每条数据重复了多少条
select MIN(id),count(id) from stang_big_fagui WHERE wangzhan="裁判文书网" group by title, author, pubtime;
四 删除数据库中重复字段
DELETE from stang_big_fagui where wangzhan="裁判文书网" AND id not in (SELECT a.c from(select MIN(b.id) as c from stang_big_fagui b WHERE b.wangzhan="裁判文书网" group by b.title,b.author,b.pubtime) a);
