Sql约束方法返回假值

Question

我在 sql 中的约束方法上遇到问题。

这是我的表格

CREATE TABLE [relations].[CompoundKey_Contacts](
    [compoundId] [varchar](32) NOT NULL,
    [companyId] [varchar](32) NULL,
    [personId] [varchar](32) NULL,
    [contactInfoId] [varchar](32) NOT NULL)

当您向该表格添加一行时，它应该检查该个人和公司的组合是否已存在于该表格中。为此，我使用约束函数

Constraint

ALTER TABLE [relations].[CompoundKey_Contacts]  WITH NOCHECK ADD  CONSTRAINT [CK_CompoundKey_Contacts] CHECK  (([relations].[doesThisCompoundKeyExist]([personId],[companyId])='NO'))
GO

ALTER TABLE [relations].[CompoundKey_Contacts] CHECK CONSTRAINT [CK_CompoundKey_Contacts]
GO

Function

CREATE function [relations].[doesThisCompoundKeyExist](
    @personId varchar(32),
    @companyId varchar(32)
)
returns varchar(3)
as
begin
    declare @exists varchar(32)

    if(@companyId is null and @personId is null)
      set @exists = 'YES'
    else if(@personId is null)
        if exists(select compoundId from relations.CompoundKey_Contacts where personId is null AND companyId = @companyId)
            set @exists = 'YES' 'This is where to code enters, but it should come to the else and return 'NO'
        else
            set @exists = 'NO'
    else if(@companyId is null)
        if exists(select compoundId from relations.CompoundKey_Contacts where personId = @personId AND companyId is null)
            set @exists = 'YES'
        else
            set @exists = 'NO'
    else if exists(
        select compoundId from relations.CompoundKey_Contacts where personId = @personId AND companyId = @companyId
        )
        set @exists = 'YES'
    else
        set @exists = 'NO'
    return @exists
end;

我的插入语句失败

insert into relations.CompoundKey_Contacts (companyId, contactInfoId, personId, compoundId) values ('COM-000015945', 'INF-000144406', null, 'CPK-000000067');

问题是这样的。当我在具有唯一插入的表上运行插入时，它仍然失败。我当然已经通过 select 语句检查了它依赖的唯一性。有趣的部分来了。当我调试它并检查它失败的位置并分解该代码部分并在不处于函数中的情况下自由运行它时，它的行为应该如此，因此如果它不在函数中运行，则以下代码可以工作

if exists(select compoundId from relations.CompoundKey_Contacts where personId is null AND companyId = 'COM-000015945')
                print 'YES'
            else
                print 'NO' 'Returns NO as it should.

这是错误消息我明白

The INSERT statement conflicted with the CHECK constraint "CK_CompoundKey_Contacts". The conflict occurred in database "domas", table "relations.CompoundKey_Contacts".
The statement has been terminated.

我在 Sql Server 2012 和 Sql Server 'DENALI' CTP3 上运行它

Answer 1

在检查约束中使用 UDF 不会可靠地工作，如您所见，

如果需要额外的逻辑，请在计算列上使用唯一约束

ALTER TABLE CompoundKey_Contacts
    ADD CompoundKey AS ISNULL(personID, 'NOPERSONID') + ISNULL(companyId, 'NOCOMPANYID');
ALTER TABLE CompoundKey_Contacts WITH CHECK
    ADD CONSTRAINT UQ_CompoundKey_Contacts_CompoundKey UNIQUE (CompoundKey);

或简单的唯一约束

ALTER TABLE CompoundKey_Contacts WITH CHECK
    ADD CONSTRAINT UQ_CompoundKey_OtherUnique UNIQUE (personID, companyId);

Answer 2

在 personId,companyId 上创建唯一约束或唯一索引。

不要尝试为此使用带有 UDF 的检查约束，因为它效率低下并且无论如何都难以获得正确结果。