用触发器是很好的方法: USE pubs IF EXISTS (SELECT name FROM sysobjects WHERE name = 'employee_insupd' AND type = 'TR') DROP TRIGGER employee_insupd GO CREATE TRIGGER employee_insupd ON employee FOR INSERT, UPDATE AS /* Get the range of level for this job type from the jobs table. */ DECLARE @min_lvl tinyint, @max_lvl tinyint, @emp_lvl tinyint, @job_id smallint SELECT @min_lvl = min_lvl, @max_lvl = max_lvl, @emp_lvl = i.job_lvl, @job_id = i.job_id FROM employee e INNER JOIN inserted i ON e.emp_id = i.emp_id JOIN jobs j ON j.job_id = i.job_id IF (@job_id = 1) and (@emp_lvl <> 10) BEGIN RAISERROR ('Job id 1 expects the default level of 10.', 16, 1) ROLLBACK TRANSACTION END ELSE IF NOT (@emp_lvl BETWEEN @min_lvl AND @max_lvl) BEGIN RAISERROR ('The level for job_id:%d should be between %d and %d.', 16, 1, @job_id, @min_lvl, @max_lvl) ROLLBACK TRANSACTION END
可以呀!但你:declare @ table(a datetime default(getdate()),b int) insert @ values(getdate(),3) select * from @ select * from @ select * from @ update @ set b=7,a=default select * from @
里说到触发器的编写
不过,如果数据量大,不提倡用触发器,还不如直接用语句赋值
create table tb_xxx
(
id ...
LastUpdated datetime default(GetDate())
)这样有没有问题?
USE pubs
IF EXISTS (SELECT name FROM sysobjects
WHERE name = 'employee_insupd' AND type = 'TR')
DROP TRIGGER employee_insupd
GO
CREATE TRIGGER employee_insupd
ON employee
FOR INSERT, UPDATE
AS
/* Get the range of level for this job type from the jobs table. */
DECLARE @min_lvl tinyint,
@max_lvl tinyint,
@emp_lvl tinyint,
@job_id smallint
SELECT @min_lvl = min_lvl,
@max_lvl = max_lvl,
@emp_lvl = i.job_lvl,
@job_id = i.job_id
FROM employee e INNER JOIN inserted i ON e.emp_id = i.emp_id
JOIN jobs j ON j.job_id = i.job_id
IF (@job_id = 1) and (@emp_lvl <> 10)
BEGIN
RAISERROR ('Job id 1 expects the default level of 10.', 16, 1)
ROLLBACK TRANSACTION
END
ELSE
IF NOT (@emp_lvl BETWEEN @min_lvl AND @max_lvl)
BEGIN
RAISERROR ('The level for job_id:%d should be between %d and %d.',
16, 1, @job_id, @min_lvl, @max_lvl)
ROLLBACK TRANSACTION
END
insert @ values(getdate(),3)
select * from @
select * from @
select * from @
update @ set b=7,a=default
select * from @
我试验了SQL里的timestamp类型,解决了自动更新标记问题,但它保存的不是时间,是一个整数,能不能规定timestamp的格式?
希望高手给个答案。