sql function

create table ClassDemo(ClassID int primary key identity(1,1),ClassName nvarchar(50))insert into ClassDemo(ClassName) values('一班');insert into ClassDemo(ClassName) values('二班');select * from ClassDemo;create table StudentDemo(StudentID int primary key identity(1,1),StudentName nvarchar(50),ClassID int)insert into StudentDemo(StudentName,ClassID)values('学生1',1);insert into StudentDemo(StudentName,ClassID)values('学生2',1);insert into StudentDemo(StudentName,ClassID)values('学生3',2);select * from StudentDemo;--表值函数create function fun_student(@ClassID int)--参数returns table--返回tableasreturn(select * from StudentDemo where ClassID=@ClassID)--测试select * from fun_student(1);select * from fun_student(1) where StudentID=1;--标量函数create function fun_name(@StudentID int)returns nvarchar(50)as begindeclare @StudentName nvarchar(50)select @StudentName=StudentName from StudentDemo where StudentID=@StudentIDreturn (@StudentName)endselect dbo.fun_name(1);select * from StudentDemo where StudentName= dbo.fun_name(1);