单双号限行，今天是否绿色出行

要判断车牌是否符合单双号出行。

这样得获取车牌最后一位数字是什么？

SET ANSI_NULLS ON
GO
SET QUOTED_IDENTIFIER ON
GO
-- =============================================
-- Author:      Insus.NET
-- Blog:        https://insus.cnblogs.com
-- Create date: 2019-06-02
-- Update date: 2019-06-02
-- Description: 返回字符中最后一位数字
-- =============================================
 CREATE FUNCTION [dbo].[svf_LicensePlateTailNumber]
 (
    @number VARCHAR(8)
 )
 RETURNS INT
 AS
 BEGIN
    DECLARE @rtn_num INT
    IF LEN(ISNULL(@number,'')) > 0
    BEGIN
        DECLARE @l INT = LEN(TRIM(LTRIM(@number)))        
        WHILE @l >= 0
        BEGIN
            DECLARE @char CHAR(1) = SUBSTRING(@number,@L,1)
            IF @char LIKE '%[0-9]%'
            BEGIN
                SET @rtn_num = CAST(@char AS INT)
                BREAK;
            END                    
        SET @l = @l - 1
        END
    END
    RETURN @rtn_num
 END

 GO

再写另外一个函数，判断数字是否为偶数：

《判断数字是否为奇数或偶数》https://www.cnblogs.com/insus/p/10965118.html

现在，我们准备一些车牌，省略了前缀：

CREATE TABLE [dbo].[plate_number]
(
    [Number] VARCHAR(8)
)
GO
INSERT INTO [dbo].[plate_number] ([Number]) VALUES
 ('E124J'),
 ('S19J3'),
 ('88888'),
 ('55555'),
 ('2312H'),
 ('WE1AB')
 GO

准备好函数与数据，那我们开始进行查询：

;WITH cte_a AS
(
    SELECT [Number],[dbo].[svf_LicensePlateTailNumber]([Number]) AS [尾号] FROM [dbo].[plate_number]
)
, cte_b AS
(
    SELECT [Number], [尾号],CASE WHEN [dbo].[svf_IsEven]([尾号]) = 1 THEN N'双号' ELSE N'单号' END AS [单双号] ,
    CASE WHEN [dbo].[svf_IsEven]([尾号]) = [dbo].[svf_IsEven](DAY(CURRENT_TIMESTAMP)) THEN '通行' ELSE N'限行' END AS [是否可通行] FROM cte_a
)
SELECT [Number],[尾号],[单双号],[是否可通行] FROM cte_b

运行得到的结果，测试的日期为2019-06-02：