Question

我试图在nchar(1)类型列中使用like运算符，下面是我的存储过程：

Create procedure [dbo].[CouponSearch]
(
@DiscountType nchar(1)
)as
begin
set nocount on
Select Couponcode from tblCoupons where DiscountType like '%'+@DiscountType+'%'
set nocount off
end

我在表 tblCoupons 中有2条记录，但我调用proc CouponSearch ''它会返回0条记录。 TIA。

我也试过以下但不能正常工作。

 Select Couponcode from tblCoupons where DiscountType like N'%'+@DiscountType+'%'

Answer 1

您正在寻找处理IIF以及''

的NULL条件

select * from tblCoupons  
where DiscountType = IIF(@DiscountType = '' OR @DiscountType IS NULL,DiscountType,@DiscountType)

因此，您的程序变为：

Createprocedure [dbo].[CouponSearch]
(
@DiscountType nchar(1)
)as
begin
set nocount on
Select Couponcode from tblCoupons where DiscountType = IIF(@DiscountType = '' OR @DiscountType IS NULL,DiscountType,@DiscountType)
set nocount off
end

Answer 2

或者这个，用于检查空值和空字符串。

示例来源

        CREATE TABLE TBLCOUPONS
            (
              Couponid INT ,
              Couponcode VARCHAR(10) ,
              DiscountType NCHAR(1) ,
              Discount INT
            )

        INSERT  TBLCOUPONS
                ( Couponid, Couponcode, DiscountType, Discount )
        VALUES  ( 1, 'JT5326', '$', 5 ),
                ( 2, 'CY1990', '%', 9 )

        GO

PROCEDURE

        CREATE PROCEDURE [dbo].[CouponSearch] ( @DiscountType NCHAR(1) )
        AS
            BEGIN

                IF ( @DiscountType = '' )
                    BEGIN
                        SET @DiscountType = NULL
                    END

                SELECT  Couponcode
                FROM    tblCoupons
                WHERE   DiscountType = ISNULL(@DiscountType, DiscountType)
            END
            GO

EXECUTION

    EXEC [CouponSearch] '%'
        GO
        EXEC [CouponSearch] '$'
        GO
        EXEC [CouponSearch] ''
        GO
        EXEC [CouponSearch] NULL
        GO

结果

         ------------------EXEC [CouponSearch] '%'
        Couponcode
        ----------
        CY1990

        (1 row(s) affected)

         ------------------EXEC [CouponSearch] '$'
        Couponcode
        ----------
        JT5326

        (1 row(s) affected)

         -------------------EXEC [CouponSearch] ''
        Couponcode
        ----------
        JT5326
        CY1990

        (2 row(s) affected)

        -------------------EXEC [CouponSearch] NULL
        Couponcode
        ----------
        JT5326
        CY1990

        (2 row(s) affected)

Answer 3

IIF（）函数，如果您使用的是SQL Server 2012：

Select Couponcode from tblCoupons where DiscountType = IIF(ISNULL(@DiscountType,'') = '', DiscountType, @DiscountType)

您可以使用较低版本的CASE语句

Select Couponcode from tblCoupons where DiscountType = CASE WHEN ISNULL(@DiscountType,'') = '' THEN DiscountType ELSE @DiscountType END

Answer 4

你也可以试试这个：

DECLARE @DiscountType nchar(1)

SELECT COUPONCODE 
FROM TBLCOUPONS 
WHERE CASE WHEN COALESCE(@DISCOUNTTYPE,'')='' THEN 1 ELSE 0 END=1  OR DISCOUNTTYPE = @DISCOUNTTYPE

如何在SQL Server中使用类似运算符的nchar

4 个答案: