SQL SERVER触发器问题

定义一个触发器，为教师表TEACHER定义完整性规则“教授的工资不得低于4000元，如果低于4000 元，自动改为4000元”。 

CREATE TRIGGER Insert_Or_Update_Sal
BEFORE INSERT OR UPDATE ON Teacher
FOR EACH ROW
AS BEGIN
IF(new.Job=‘教授’)AND(new.Sal<4000) THEN
new.Sal:=4000;
END IF;
END;

课本上的例子是oracle数据库的写法，粘贴到sql server数据库上时会报错！百度上的许多改法都行不通，自己去图书馆查资料码了SQL SERVER的触发器的写法。

--新建teacher表
CREATE TABLE TEACHER(
TNO INT,
TNAME CHAR(10),
TJOB NVARCHAR(10),
SALARY INT
);
--BEFORE级触发器
ALTER TRIGGER insert_or_update_sal
ON TEACHER
INSTEAD OF UPDATE,INSERT
AS
DECLARE @TNO INT,
@TNAME CHAR(10),
@TJOB NVARCHAR(10),
@SALARY INT
BEGIN
SELECT @TNO = TNO, @TNAME =TNAME, @TJOB = TJOB, @SALARY = SALARY FROM inserted;--从inserted表中取出修改的数据
IF EXISTS(SELECT * FROM TEACHER WHERE TNO=(SELECT TNO FROM INSERTED)) AND ( @TJOB = N'教授') AND (@SALARY < 4000)--当修改表中教授工资时，如果小于4000，则修改成4000
BEGIN
update TEACHER set SALARY = 4000 where Teacher.TNO = @TNO;
END
ELSE IF EXISTS(SELECT * FROM TEACHER WHERE TNO=(SELECT TNO FROM INSERTED))--否则，则按原操作修改
BEGIN
UPDATE TEACHER set TNAME=@TNAME, TJOB=@TJOB, SALARY = @SALARY WHERE TEACHER.TNO = @TNO;
END
ELSE IF NOT EXISTS(SELECT * FROM TEACHER WHERE TNO=(SELECT TNO FROM INSERTED)) AND ( @TJOB = N'教授') AND (@SALARY < 4000)--当插入教授数据时，如果工资小于4000，则修改成4000
BEGIN
INSERT TEACHER VALUES(@TNO, @TNAME, @TJOB, 4000);
END
ELSE IF NOT EXISTS(SELECT * FROM TEACHER WHERE TNO=(SELECT TNO FROM INSERTED))--否则，则按原操作插入
BEGIN
INSERT TEACHER VALUES(@TNO, @TNAME, @TJOB, @SALARY);
END
END

上面代码已经过测试，update&insert操作都没问题！希望能帮到后来学习数据库相关课程的同学。