如何创建与身份类似的自定义触发器或计算列？
我有两个字段需要自动递增但按特定顺序排列： 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"
如果我要在表格中插入更多记录，请执行以下操作：
INSERT INTO DRAWINGS (INFO) VALUES ("Draw5")
INSERT INTO DRAWINGS (ID,INFO) VALUES (3,"Draw3Edit")
我的表格想：
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：
我认为我接近我想要的东西：
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
答案 0 :(得分：0)
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或客户端程序中以程序方式分配序数值。
答案 1 :(得分：0)
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