t-sql：將數據類型varchar轉換爲數字在語句中時出錯

Question

我無法理解錯誤，因爲我沒有試圖將數字變量@FQTROQ轉換爲數字。

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 

任何幫助？感謝

Answer 1

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 

你需要轉換DECIMAL爲VARCHAR使來自CASE語句的輸出具有相同的輸出值。

Answer 2

你需要這樣做：

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

，因爲從一列返回的值需要匹配，SQL Server將嘗試將VARCHAR轉換爲數值，而不是其他方式，這是什麼你可能想要。

這是什麼命名約定，順便說一句？

Answer 3

這是因爲你有兩個不同類型的變量，即使你只是試圖返回其中的一個值爲「Numero_Troquel」，它們必須是兼容的類型。它所做的是試圖將@FQTROQ變量轉換爲DECIMAL。

你會要麼需要做的：

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

或者......

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