sql-server – 在sql中将varchar值转换为数据类型int时转换失败

我写了商店程序,它应该返回如下的值：

J1
J2
J3

我有一个名为Journal_Entry的表.当表的行数为0时,它给出结果J1,但随着行数的增加,它显示错误 –

"Conversion failed when converting the varchar value 'J' to data type int."

#here Voucher_No是要保存的结果的列.

代码如下 –

CREATE PROC [dbo].[getVoucherNo]
AS
BEGIN
    DECLARE @Prefix VARCHAR(10)='J'
    DECLARE @startFrom INT=1
    DECLARE @maxCode VARCHAR(100)
    DECLARE @sCode INT
    IF((SELECT COUNT(*) FROM dbo.Journal_Entry) > 0)
    BEGIN
        SELECT @maxCode = CAST(MAX(CAST(SUBSTRING(Voucher_No,LEN(@startFrom)+1,LEN(Voucher_No)- LEN(@Prefix)) AS INT)) AS varchar(100)) FROM dbo.Journal_Entry;
        SET @sCode=CAST(@maxCode AS INT)
        SELECT  @Prefix + LEN(CAST(@maxCode AS VARCHAR(10))+1) + CAST(@maxCode AS VARCHAR(100))
    END
    ELSE
    BEGIN
        SELECT(@Prefix + CAST(@startFrom AS VARCHAR)) 
    END

END

解决方法

SELECT  @Prefix + LEN(CAST(@maxCode AS VARCHAR(10))+1) + CAST(@maxCode AS VARCHAR(100))

请改用它

SELECT  @Prefix + CAST(LEN(CAST(@maxCode AS VARCHAR(10))+1) AS VARCHAR(100)) + CAST(@maxCode AS VARCHAR(100))

完整代码：

CREATE PROC [dbo].[getVoucherNo]

AS

BEGIN

    DECLARE @Prefix VARCHAR(10)='J'

    DECLARE @startFrom INT=1

    DECLARE @maxCode VARCHAR(100)

    DECLARE @sCode INT

    IF((SELECT COUNT(*) FROM dbo.Journal_Entry) > 0)
    BEGIN
        SELECT @maxCode = CAST(MAX(CAST(SUBSTRING(VoucharNo,LEN(VoucharNo)- LEN(@Prefix)) AS INT))+1 AS varchar(100)) FROM dbo.Journal_Entry;
        SET @sCode=CAST(@maxCode AS INT)
        SELECT  @Prefix + CAST(LEN(CAST(@maxCode AS VARCHAR(10))+1) AS VARCHAR(100)) + CAST(@maxCode AS VARCHAR(100))
    END
    ELSE
    BEGIN
        SELECT(@Prefix + CAST(@startFrom AS VARCHAR)) 
    END
END

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