Sql server SQL:左联接和求和：算术溢出将表达式转换为数据类型int时出错

我有一个疑问：

select p.UserName, sum(b.PercentRials) as amount, sum(r.Amount) as Pays
from bills b inner join UserProfiles p on b.PayerUserName=p.UserName
left outer join PayReceipts r on p.UserName=r.UserName
where p.[Percent]>0 and b.PayDate>'2014-11-20'
group by p.UserName

我在运行时遇到此错误：

Msg 8115, Level 16, State 2, Line 1
Arithmetic overflow error converting expression to data type int.
Warning: Null value is eliminated by an aggregate or other SET operation.

我可以理解外部联接导致此错误，因为当我删除最后一个和时，它运行正常。但我记得我做过这样的查询，并在外部联接表上得到求和的

NULL

---

我能做什么？

如果你在金融公司工作

sum(r.Amount) as Pays

很可能超过20亿这个微不足道的整数极限。您可以强制转换为更大的变量类型：

试试这个

select p.UserName, sum(b.PercentRials) as amount, sum(CAST (r.Amount AS BIGINT)) as Pays
from bills b inner join UserProfiles p on b.PayerUserName=p.UserName
left outer join PayReceipts r on p.UserName=r.UserName
where p.[Percent]>0 and b.PayDate>'2014-11-20'
group by p.UserName

---

SUM

中的表达式类型决定了输出的类型。因此，当总和超过整数限制时，您将收到此错误。要将数据视为整数而不产生错误，您需要将

amount

列转换为

BIGINT

，因此总和的类型为

BIGINT

这个警告误导了我。我认为外部连接是原因，我希望

pays

列的值要小得多。谢谢

select p.UserName, sum(b.PercentRials) as amount, sum(CAST (r.Amount AS BIGINT)) as Pays
from bills b inner join UserProfiles p on b.PayerUserName=p.UserName
left outer join PayReceipts r on p.UserName=r.UserName
where p.[Percent]>0 and b.PayDate>'2014-11-20'
group by p.UserName