select sn,count(*) from T_claim_datadtlc group by sn having count(*)>1 order by sn desc;
group by + 列名 就是按照这个列分组
having count(*)>1 分组后计算记录数,且记录数〉1
select sn,count(*) from T_claim_datadtlc group by sn having count(*)>1 order by sn desc;
group by + 列名 就是按照这个列分组
having count(*)>1 分组后计算记录数,且记录数〉1