判斷字串是否為純數字，負數不算。如'00012','54585','1000'

SET ANSI_NULLS ON
GO
SET QUOTED_IDENTIFIER ON
GO
CREATE FUNCTION [dbo].[svf_IsNumeric] 
(
  @string NVARCHAR(MAX)
) RETURNS BIT  --函式返BIT資料型別，是數字返回1，非數字返回0。
AS
BEGIN
    DECLARE @rtv BIT = 1   
    DECLARE @str NVARCHAR(MAX) = LTRIM(RTRIM
 
(ISNULL(@string,''))) --去除前後空格，如果為NULL轉為''
    
    DECLARE @start INT = 1; 
    DECLARE @end INT = LEN(@str) --獲取字串長度
     
    WHILE (@start <= @end)  --迴圈字串每一個字元
    BEGIN
        DECLARE @Numeric VARCHAR(1) = ''
    
        SET @Numeric = SUBSTRING(@str, @start, @start + 1) -- 每迴圈一次，從左邊獲取一位字元
 

 
        IF ASCII(@Numeric) >= 48 AND ASCII(@Numeric) <= 57  --如果是數字
        BEGIN
            SET @start = @start + 1;
            CONTINUE  --繼續迴圈    
        END
        ELSE
        BEGIN
            SET @rtv = 0
            BREAK  --跳出迴圈
        END
    END
    
    RETURN @rtv
 

END

建立一個例子來演示：

CREATE TABLE [dbo].[uTable] ([col1] NVARCHAR(20),[col2] NVARCHAR(20),[col3] NVARCHAR(20),[col4] NVARCHAR(20),[col5] NVARCHAR(20),[col6] NVARCHAR(20),[col7] NVARCHAR(20))
GO

INSERT INTO [dbo].[uTable] ([col1],[col2],[col3],[col4],[col5],[col6],[col7]) 
VALUES ('0.455','000435','SF46DG','4000','$%9KJ','-0034','-8554')
GO


SELECT [dbo].[svf_IsNumeric] ([col1]) AS [col1],
[dbo].[svf_IsNumeric] ([col2]) AS [col2],
[dbo].[svf_IsNumeric] ([col3]) AS [col3],
[dbo].[svf_IsNumeric] ([col4]) AS [col4],
[dbo].[svf_IsNumeric] ([col5]) AS [col5],
[dbo].[svf_IsNumeric] ([col6]) AS [col6],
[dbo].[svf_IsNumeric] ([col7]) AS [col7]
FROM [dbo].[uTable] 
GO