29. 查询某个字段重复的记录

这里是查询tcalendar表ID值相同的记录

select * from tcalendar where id in (
　　select id from tcalendar t where t.id in (
　　　　select t1.id from tcalendar t1 group by t1.id having count(*) >1
　　)
) order by id asc