MySQL 查重复单号和删重复单号

SELECT ID,BillCode from downpackage_1 where BillCode in
(select BillCode from downpackage_1
group by BillCode having(count(BillCode)>1)
) ORDER BY ID ;

DELETE from downpackage where ID in (
SELECT a.ID FROM (
select MIN(ID) as ID from downpackage
group by BillCode having count(BillCode)>1 ) as a
);