t_printmould ：表名；
rowid ：oracle从8i开始引进object的概念后的rowid，即扩展（extended）的rowid；
min(rowid) ：删除rowid大的一条，保留小的一条rowid；
删除重复id记录
delete from platform.t_printmould where mouldid in (select mouldid from platform.t_printmould group by mouldid having count(mouldid) > 1) and rowid not in (select min(rowid) from platform.t_printmould group by mouldid having count(mouldid) > 1);
扩展:
查询重复id记录
select mouldid from platform.t_printmould group by mouldid having count(mouldid) > 1