Apa cara yang benar untuk memastikan entri unik dalam desain basis data temporal?

Saya mengalami masalah dengan desain database temporal. Saya perlu tahu cara memastikan saya hanya memiliki satu catatan aktif untuk jangka waktu tertentu untuk toko. Saya telah membaca jawaban ini , tetapi saya khawatir saya tidak dapat membungkus kepala saya bagaimana pemicu akan bekerja. Khususnya, bagaimana saya akan bekerja yang memicu ke saya yang sudah ada yang mencegah pembaruan ke catatan, dan menyisipkan catatan baru sebagai gantinya. Masalah saya yang sebenarnya adalah bahwa saya tidak tahu bagaimana mencegah Toko memiliki lebih dari satu tanggal efektif ketika tanggal selesai adalah nol. (Yaitu mencegah 2 catatan aktif untuk toko).

Ini yang saya miliki, tetapi memungkinkan saya untuk memasukkan catatan baru untuk toko dengan tanggal efektif yang berbeda.

Definisi Tabel:

/****** Object:  Table [PCR].[Z_STORE_TEAM]    Script Date: 05/09/2014 13:05:57 ******/
IF  EXISTS (SELECT * FROM sys.objects WHERE object_id = OBJECT_ID(N'[Z_STORE_TEAM]') AND type in (N'U'))
DROP TABLE [Z_STORE_TEAM]
GO

IF NOT EXISTS (SELECT * FROM sys.objects WHERE object_id = OBJECT_ID(N'[Z_STORE_TEAM]') AND type in (N'U'))
BEGIN
CREATE TABLE [Z_STORE_TEAM](
    [STORENUM] [int] NOT NULL,
    [TEAM] [varchar](10) NULL,
    [EFFECTIVE] [date] NOT NULL,
    [FINISHED] [date] NULL,
PRIMARY KEY CLUSTERED 
(
    [STORENUM] ASC,
    [EFFECTIVE] ASC
)WITH (PAD_INDEX  = OFF, STATISTICS_NORECOMPUTE  = OFF, IGNORE_DUP_KEY = OFF, ALLOW_ROW_LOCKS  = ON, ALLOW_PAGE_LOCKS  = ON) ON [PRIMARY]
) ON [PRIMARY]
END
GO

Contoh data:

INSERT [Z_STORE_TEAM] ([STORENUM], [TEAM], [EFFECTIVE], [FINISHED]) VALUES (1, N'1', CAST(0x01380B00 AS Date), CAST(0x81380B00 AS Date))
INSERT [Z_STORE_TEAM] ([STORENUM], [TEAM], [EFFECTIVE], [FINISHED]) VALUES (1, N'2', CAST(0x81380B00 AS Date), NULL)
INSERT [Z_STORE_TEAM] ([STORENUM], [TEAM], [EFFECTIVE], [FINISHED]) VALUES (2, N'1', CAST(0x01380B00 AS Date), NULL)
INSERT [Z_STORE_TEAM] ([STORENUM], [TEAM], [EFFECTIVE], [FINISHED]) VALUES (2, N'2', CAST(0x20380B00 AS Date), NULL)

Alih-alih Perbarui Pemicu:

CREATE TRIGGER [tr_ZStoreTeam_update] 
   ON  [Z_STORE_TEAM]
   INSTEAD OF UPDATE
AS 
BEGIN
    -- SET NOCOUNT ON added to prevent extra result sets from
    -- interfering with SELECT statements.
    SET NOCOUNT ON;

    -- Insert statements for trigger here
    INSERT INTO PCR.Z_STORE_TEAM(STORENUM,TEAM,EFFECTIVE)
    SELECT I.STORENUM,I.TEAM,GETDATE() AS EFFECTIVE
    FROM inserted I
    INNER JOIN PCR.Z_STORE_TEAM ST
        ON I.STORENUM = ST.STORENUM

    UPDATE ST
    SET FINISHED = GETDATE()
    FROM PCR.Z_STORE_TEAM ST
    INNER JOIN inserted I
        ON ST.STORENUM = I.STORENUM
        AND ST.EFFECTIVE = I.EFFECTIVE
END

GO

— Bebek karet
sumber

Cara teraman untuk melakukan ini adalah dengan menegakkan aturan bisnis Anda menggunakan batasan integritas referensial bawaan, seperti yang dijelaskan Alexander Kuznetsov dalam artikelnya, "Menyimpan interval waktu tanpa tumpang tindih" .

Menerapkan teknik yang terdaftar di sana ke tabel sampel Anda menghasilkan skrip berikut:

CREATE TABLE [Z_STORE_TEAM](
    [STORENUM] [int] NOT NULL,
    [TEAM] [varchar](10) NULL,
    [EFFECTIVE] [date] NOT NULL,
    [FINISHED] [date] NULL,
    PRIMARY KEY CLUSTERED 
    (
        [STORENUM] ASC,
        [EFFECTIVE] ASC
    )
) ON [PRIMARY];

INSERT [Z_STORE_TEAM] 
    ([STORENUM], [TEAM], [EFFECTIVE], [FINISHED]) 
VALUES 
    (1, N'1', CAST(0x01380B00 AS Date), CAST(0x81380B00 AS Date)),
    (1, N'2', CAST(0x81380B00 AS Date), NULL),
    (2, N'1', CAST(0x01380B00 AS Date), NULL);

Modifikasi:

-- New column to hold the previous finish date
ALTER TABLE dbo.Z_STORE_TEAM 
ADD PreviousFinished date NULL;
GO
-- Populate the previous finish date
UPDATE This
SET PreviousFinished = Previous.FINISHED
FROM dbo.Z_STORE_TEAM AS This
CROSS APPLY
(
    SELECT TOP (1) 
        Previous.FINISHED
    FROM dbo.Z_STORE_TEAM AS Previous
    WHERE 
        Previous.STORENUM = This.STORENUM
        AND Previous.FINISHED <= This.EFFECTIVE
    ORDER BY 
        Previous.FINISHED DESC
) AS Previous;
GO
ALTER TABLE dbo.Z_STORE_TEAM 
ADD CONSTRAINT UQ_STORENUM_PreviousFinished
UNIQUE (STORENUM, PreviousFinished);
GO
ALTER TABLE dbo.Z_STORE_TEAM
ADD CONSTRAINT CK_PreviousFinished_NotAfter_Effective
CHECK (PreviousFinished = EFFECTIVE);
GO
ALTER TABLE dbo.Z_STORE_TEAM
ADD CONSTRAINT UQ_STORENUM_FINISHED
UNIQUE (STORENUM, FINISHED);
GO
ALTER TABLE dbo.Z_STORE_TEAM
ADD CONSTRAINT FK_STORENUM_PreviousFinished
FOREIGN KEY (STORENUM, PreviousFinished)
REFERENCES dbo.Z_STORE_TEAM (STORENUM, FINISHED);
GO
ALTER TABLE dbo.Z_STORE_TEAM
ADD CONSTRAINT CK_EFFECTIVE_Before_FINISHED
CHECK (EFFECTIVE < FINISHED);

Upaya memasukkan baris keempat data sampel sekarang gagal dengan pesan kesalahan:

INSERT [Z_STORE_TEAM] 
    ([STORENUM], [TEAM], [EFFECTIVE], [FINISHED]) 
VALUES 
    (2, N'2', '20140201', NULL);

Pesan eror

Baca artikel Alex untuk memahami bagaimana kendala ini memastikan data tabel Anda akan selalu valid. Memiliki serangkaian kendala yang menegakkan integritas data Anda berarti tidak ada kode pemicu yang diperlukan.