1.查找表a中有而表b中没有的数据
select djbh from zj_splzyjb a where not exists (select djbh from zj_splzb b where a.djbh=b.djbh)
2.搜索表a中的djbh,xh两个字段不唯一的记录即重复记录
select djbh||'-'||xh as djbhxh,count(djbh) from zj_fybxbd b group by djbh,xh