TSQL：创建自定义标识列（修订数据库）

Question

如何创建与身份类似的自定义触发器或计算列？

我有两个需要自动递增但按特定顺序的字段：ID 和 REV。

DRAWINGS
ID    | REV   | INFO
------+-------+------
1     | 0     | "Draw1"
2     | 0     | "Draw2"
2     | 1     | "Draw2Edit"
2     | 2     | "Draw2MoreEdit"
3     | 0     | "Draw3"
4     | 0     | "Draw4"

如果我要在表中插入更多记录，例如：

INSERT INTO DRAWINGS (INFO) VALUES ("Draw5")
INSERT INTO DRAWINGS (ID,INFO) VALUES (3,"Draw3Edit")

我的表将需要：

DRAWINGS
ID    | REV   | INFO
------+-------+------
1     | 0     | "Draw1"
2     | 0     | "Draw2"
2     | 1     | "Draw2Edit"
2     | 2     | "Draw2MoreEdit"
3     | 0     | "Draw3"
3     | 1     | "Draw3Edit"      --NEW ROW
4     | 0     | "Draw4"
5     | 0     | "Draw5"          --NEW ROW

伪代码

-- IF ID==NULL AND REV==NULL THEN IT IS A NEW DRAWING
IF INSERTED.ID IS NULL AND INSERTED.REV IS NULL 
   ID = SELECT MAX(ID)+1 FROM DRAWINGS
   REV = 0
   --INSERT HERE STATEMENT HERE
ELSE
   -- IF ID!=NULL AND REV==NULL THEN IT IS A NEW REVISION
   IF INSERTED.ID IS NOT NULL AND INSERTED.REV IS NULL
       -- EXTRA CHECK TO ENSURE DRAWING ACTUALLY EXISTS
       IF EXISTS(INSERTED.ID)
           REV = SELECT MAX(REV) + 1 FROM DRAWINGS WHERE ID = INSERTED.ID
           --INSERT HERE STATEMENT HERE
       ELSE
           --DRAWING DOES NOT ACTUALLY EXIST
           GOTO ERROR
   ELSE
       --REV IS NOT NULL (REVISIONS ARE A COMPUTED VALUE ERROR)
       GOTO ERROR

注意：

• 我使用的是SQL Server 2000。
• 该表仅用于插入。

我想我已经接近我想要的了：

DROP TABLE DRAW

GO

CREATE TABLE DRAW
(
    ID INT DEFAULT(0), 
    REV INT DEFAULT(-1), 
    INFO VARCHAR(10), 
    PRIMARY KEY(ID, REV)
)

GO

CREATE TRIGGER TRIG_DRAW ON DRAW
FOR INSERT
AS
BEGIN
    DECLARE @newId INT,
            @newRev INT,
            @insId INT,
            @insRev INT

    SET TRANSACTION ISOLATION LEVEL READ COMMITTED
    BEGIN TRANSACTION

    SELECT @insId = ID FROM inserted
    SELECT @insRev = REV FROM inserted

    PRINT 'BEGIN TRIG'
    PRINT @insId
    PRINT @insRev
    PRINT @newId
    PRINT @newRev


    --IF ID=0 THEN IT IS A NEW ID
    IF @insId <=0
    BEGIN
        --NEW DRAWING ID=MAX+1 AND REV=0
        SELECT @newId = COALESCE(MAX(ID), 0) + 1 FROM DRAW
        SELECT @newRev = 0
    END
    ELSE
    --ELSE IT IS A NEW REV
    BEGIN
        --CHECK TO ENSURE ID EXISTS
        IF EXISTS(SELECT * FROM DRAW WHERE ID=@insId AND REV=0)
        BEGIN
            PRINT 'EXISTS'
            SELECT @newId = @insId
            SELECT @newRev = MAX(REV) + 1 FROM DRAW WHERE ID=@insID
                                                            AND   REV=-1
        END
        ELSE
        --ID DOES NOT EXIST THEREFORE NO REVISION
        BEGIN
            RAISERROR 50000 'ID DOES NOT EXIST.'
            ROLLBACK TRANSACTION
            GOTO END_TRIG
        END
    END

    PRINT 'END TRIG'
    PRINT @insId
    PRINT @insRev
    PRINT @newId
    PRINT @newRev

    SELECT * FROM DRAW

    UPDATE DRAW SET ID=@newId, REV=@newRev WHERE ID=@insId



    COMMIT TRANSACTION
    END_TRIG:
END

GO


INSERT INTO DRAW (INFO) VALUES ('DRAW1')
INSERT INTO DRAW (INFO) VALUES ('DRAW2')
INSERT INTO DRAW (ID,INFO) VALUES (2,'DRAW2EDIT1') --PROBLEM HERE
INSERT INTO DRAW (ID,INFO) VALUES (2,'DRAW2EDIT2')
INSERT INTO DRAW (INFO) VALUES ('DRAW3')
INSERT INTO DRAW (INFO) VALUES ('DRAW4')

GO

--SHOULD THROW
INSERT INTO DRAW (ID,INFO) VALUES (9,'DRAW9')

GO

SELECT * FROM DRAW

GO

Answer 1

使用时间戳将插入按正确的顺序排列，然后在选择行时在 SP 或客户端程序中按程序分配序数值。

Answer 2

DROP TABLE DRAW

GO

CREATE TABLE DRAW
(
    ID INT DEFAULT(0), 
    REV INT DEFAULT(-1), 
    INFO VARCHAR(10), 
    PRIMARY KEY(ID, REV)
)

GO

CREATE TRIGGER TRIG_DRAW ON DRAW
FOR INSERT
AS
BEGIN
    DECLARE @newId INT,
            @newRev INT,
            @insId INT,
            @insRev INT

    SET TRANSACTION ISOLATION LEVEL READ COMMITTED
    BEGIN TRANSACTION

    SELECT @insId = ID FROM inserted
    SELECT @insRev = REV FROM inserted

    --IF ID=0 THEN IT IS A NEW ID
    IF @insId <=0
    BEGIN
        --NEW DRAWING ID=MAX+1 AND REV=0
        SELECT @newId = COALESCE(MAX(ID), 0) + 1 FROM DRAW
        SELECT @newRev = 0
    END
    ELSE
    --ELSE IT IS A NEW REV
    BEGIN
        --CHECK TO ENSURE ID EXISTS (NOT COUNTING JUST INSERTED)
        IF (SELECT COUNT(*) FROM DRAW WHERE ID=@insId) > 1
        BEGIN
            SELECT @newId = @insId
            SELECT @newRev = MAX(REV) + 1 FROM DRAW WHERE ID=@insID
        END
        ELSE
        --ID DOES NOT EXIST THEREFORE NO REVISION
        BEGIN
            RAISERROR 50000 'ID DOES NOT EXIST.'
            ROLLBACK TRANSACTION
            GOTO END_TRIG
        END
    END

    UPDATE DRAW SET ID=@newId, REV=@newRev WHERE ID=@insId AND REV=-1

    COMMIT TRANSACTION
    END_TRIG:
END

GO


INSERT INTO DRAW (INFO) VALUES ('DRAW1')
INSERT INTO DRAW (INFO) VALUES ('DRAW2')
INSERT INTO DRAW (ID,INFO) VALUES (2,'DRAW2EDIT1') --PROBLEM HERE
INSERT INTO DRAW (ID,INFO) VALUES (2,'DRAW2EDIT2')
INSERT INTO DRAW (INFO) VALUES ('DRAW3')
INSERT INTO DRAW (INFO) VALUES ('DRAW4')

GO

--SHOULD THROW
INSERT INTO DRAW (ID,INFO) VALUES (9,'DRAW9')

GO

SELECT * FROM DRAW

GO