检查约束不允许我添加数据

Question

我有一个用户定义的函数，该函数返回BIT。

• 1-如果日期重叠
• 0-如果日期不重叠

我已经测试了UDF，它似乎运行正常。

这是我添加的以下检查约束：

ALTER TABLE [Gizmo] WITH CHECK ADD CONSTRAINT [CK_DateOverlap]
CHECK [dbo].[MyUserFunction]([GizmoName],[GizmoState],[BeginDate],[EndDate]) = 0;

该表中没有任何数据。当我插入新记录时，出现错误

The INSERT statement conflicted with the CHECK constraint

我手动调用UDF进行测试，它返回0。

如果UDF返回0，我希望约束添加记录。如果返回1，我不想添加它。

我想念什么？

编辑-UDF

ALTER FUNCTION [dbo].[MyUserFunction]
(
     @GizmoName AS VARCHAR(max),
     @GizmoState AS VARCHAR(max),
     @BeginDate AS DATETIME,
     @EndDate AS DATETIME

)

RETURNS BIT
AS
BEGIN
       DECLARE @Result BIT
       IF EXISTS(
                    SELECT *
                    FROM Gizmos
                    WHERE (@GizmoName = Name AND @GizmoState = [State])
                    AND (@EndDate >= EffectiveFrom AND EffectiveTo >= @BeginDate)
                    )
                    BEGIN
                        SET @Result = 1;
                    END
                    ELSE
                    BEGIN
                           SET @Result = 0;   
                    END
       RETURN @Result
END

插入

INSERT INTO Gizmos VALUES('XXX', 'CA', '1/1/2019', '12/31/2019');

Answer 1

该行已插入表中，并且约束已应用到表上。因此，数据已经可用，函数将返回1并回滚事务。因此我们需要忽略第一行，然后按预期运行。

CREATE OR ALTER FUNCTION [dbo].[MyUserFunction]
(
     @GizmoName AS VARCHAR(max),
     @GizmoState AS VARCHAR(max),
     @BeginDate AS DATETIME,
     @EndDate AS DATETIME

)

RETURNS BIT
AS
BEGIN
       DECLARE @Result BIT

       IF (SELECT COUNT(Name)
                    FROM Gizmos
                    WHERE (@GizmoName = Name AND @GizmoState = [State])
                    AND (@EndDate >= EffectiveFrom AND EffectiveTo >= @BeginDate)
                    ) > 1
                    BEGIN
                        SET @Result = 1;
                    END
                    ELSE
                    BEGIN
                           SET @Result = 0;   
                    END

                    RETURN @Result

END
GO