SQL查询帮助-重复值

你似乎想要:

select t.*
from t
where exists (select 1
              from t t2
              where t2.invoice_number = t.invoice_number and
                    t2.customer <> t.customer
             );

即,显示发票上有多个客户的发票。

通过首先查找出现在1个以上客户的所有发票号码,构建此查询对我来说是最清楚的:

select Invoice_Number from CUSTOMER_TABLE 
group by Invoice_Number having count(*) > 1;

 Invoice_Number 
----------------
 AB111

现在,在 where 条款,用于:

select * from CUSTOMER_TABLE 
where Invoice_Number in (
   select Invoice_Number from CUSTOMER_TABLE 
   group by Invoice_Number having count(*) > 1
);

 Customer | Invoice_Number
----------+---------------
 Fred     | AB111
 Fred     | AB111
 Alan     | AB111
 Alan     | AB111
 Alan     | AB111