Tsql t-sql:在then语句中将数据类型varchar转换为数字时出错

我无法理解错误，因为我没有尝试将变量@FQTROQ转换为数字

declare @FQTROQ varchar(30)
declare @FQNUTQ decimal(6,0)
set @FQTROQ = 'R-354'
set @FQNUTQ = 100

SELECT ( CASE WHEN (@FQTROQ is not null and @FQTROQ <> '')
THEN ( @FQTROQ )
ELSE ( @FQNUTQ ) END ) AS Numero_Troquel

有什么帮助吗？谢谢

您需要这样做：

SELECT ( CASE WHEN (@FQTROQ is not null and @FQTROQ <> '')
THEN ( @FQTROQ )
ELSE ( CAST(@FQNUTQ AS VARCHAR(30))) END ) AS Numero_Troquel

因为从列返回的值需要匹配，SQL Server将尝试将VARCHAR转换为数字，而不是相反，这可能是您想要的

---

顺便说一句，命名惯例是什么？

这是因为您有两个不同类型的变量，即使您只想将其中一个值作为Numero\u Troquel返回，它们也必须是兼容的类型。它正在尝试将@FQTROQ变量转换为十进制

您需要执行以下操作之一：

SELECT ( CASE WHEN (@FQTROQ is not null and @FQTROQ <> '')
THEN ( @FQTROQ )
ELSE ( CAST(@FQNUTQ AS VARCHAR(30)) ) END ) AS Numero_Troquel

或者

---

您需要将十进制转换为VARCHAR，以便CASE语句的输出具有相同的输出值。

谢谢。我不知道！非常感谢。简单的回答我不知道我遇到过类似的情况，我试图根据列内容有条件地将列转换为十进制。在我将十进制结果转换回varchar之前，我一直遇到这个错误。非常感谢！

IF (@FQTROQ is not null and @FQTROQ <> '')
    SELECT @FQTROQ AS Numero_Troquel -- this will return as a VARCHAR
ELSE
    SELECT @FQNUTQ AS Numero_Troquel -- this will return as a DECIMAL

declare @FQTROQ varchar(30)
declare @FQNUTQ decimal(6,0)
set @FQTROQ = 'R-354'
set @FQNUTQ = 100

SELECT CASE WHEN (@FQTROQ is not null and @FQTROQ <> '')
THEN @FQTROQ
ELSE CAST(@FQNUTQ AS VARCHAR(30)) END AS Numero_Troquel