ISNULL用SUM与在同一列

Question

我试着总结蒙上了列名，这样的演员：

ISNULL(SUM(CAST(VPL.Amount AS VARCHAR(10))), '') as total 

，但我得到这个错误：

Operand data type varchar is invalid for sum operator.

谢谢

Answer 1

您应该首先执行SUM部分，然后投射结果。

ISNULL(CAST(SUM([VPL].[Amount]) AS VARCHAR(10)), '') AS [total] 

Answer 2

SUM只能与NUMERIC列上。 NULL值被忽略。

CAST(SUM(VPL.Id) AS VARCHAR(10)) as total 

Answer 3

使用列数据类型在其中为列“VPL.Amount”

ISNULL(SUm(CAST(VPL.Amount AS DECIMAL)), '') as total