Enforce Unique Nullable Column With ‘IGNORE_DUP_KEY = ON’

CREATE TABLE [identigy].[patron](
	[ID] [bigint] NOT NULL,
	[DISID] [nvarchar](20) NOT NULL,
	[PKID] [nvarchar](20) NULL,
	[DISHID] [nvarchar](20) NULL,
	[FIRSTNAME] [nvarchar](250) NULL,
	[LASTNAME] [nvarchar](250) NULL,
	[CLASSIFICATION] [nvarchar](250) NULL,
	[FLAGS] [nvarchar](500) NULL,
	[SHIFTS] [nvarchar](50) NULL,
	[ACTION] [nvarchar](10) NULL,
	[ACTIVE] [bit] NOT NULL CONSTRAINT [DEFAULT_Identigy_Patron_Active]  DEFAULT ((1))
	,[DISIDnullbuster] AS (CASE WHEN [DISID] IS NULL THEN CAST(ID AS VARCHAR(20)) ELSE DISID END)
	,[PKIDnullbuster] AS (CASE WHEN [PKID] IS NULL THEN CAST(ID AS VARCHAR(20)) ELSE PKID END)
 ,CONSTRAINT [PK_Identigy_Patron] PRIMARY KEY CLUSTERED ( [ID] ASC )WITH (IGNORE_DUP_KEY = ON) ON [PRIMARY]
 ,CONSTRAINT [UX_Identigy_Patron_DISID] UNIQUE ( [DISIDnullbuster] ASC ) WITH (IGNORE_DUP_KEY = ON) ON [PRIMARY]
 ,CONSTRAINT [UX_Identigy_Patron_PKID] UNIQUE ( [PKIDnullbuster] ASC ) WITH (IGNORE_DUP_KEY = ON) ON [PRIMARY]
) ON [PRIMARY]
GO