SQL中的用户定义的标量函数

Question

I am new to SQL and am learning User Defined Functions in SQL

I have two tables and I have given the rows I have inserted to those tables.

--Table1

create table sql_exam(
exa_examid bigint not null primary key,
exa_name varchar(100) not null,
exa_maxmark decimal(5,2) not null,
exa_minmarkreqdforpass decimal(5,2) not null,
exa_examscheduletime datetime not null
)

--Rows inserted into Table1

insert into sql_exam(exa_examid,exa_name,exa_maxmark,exa_minmarkreqdforpass,exa_examscheduletime) values (1,'Maths',100,40,'2012-10-10 10:00')
insert into sql_exam(exa_examid,exa_name,exa_maxmark,exa_minmarkreqdforpass,exa_examscheduletime) values (2,'English',75,35,'2012-10-11 10:00')

--Table2

create table sql_studentmarks(
stm_studentid int not null primary key,
stm_examid bigint foreign key references sql_exam(exa_examid),
stm_mark decimal(5,2)
)

--Rows inserted into Table2
insert into sql_studentmarks(stm_studentid,stm_examid,stm_mark) values (1,1,80)
insert into sql_studentmarks(stm_studentid,stm_examid,stm_mark) values (2,1,90)
insert into sql_studentmarks(stm_studentid,stm_examid,stm_mark) values (3,1,40)
insert into sql_studentmarks(stm_studentid,stm_examid,stm_mark) values (1,2,70)
insert into sql_studentmarks(stm_studentid,stm_examid,stm_mark) values (2,2,60)
insert into sql_studentmarks(stm_studentid,stm_examid,stm_mark) values (3,2,17)

I require a help about creating Scalar functions and I need to get

1. A scalar function which will return the Student ID of the student who got highest mark in 'Maths'
2. A tabular function which will return the student ID and marks gained by the student who got highest total mark.

Am just trying to learn SQL. I have tried - "

create function fnGetMathsHightest()
returns int
as
begin
declare @st_id int
return @st_id
end



select dbo.fnGetMathsHightest() 
from sql_studentmarks 
where stm_examid=1 
group by stm_studentid 
having stm_mark=max(stm_mark)

for the first one. It does not look good.

Answer 1

It looks like this what you want for 1.

CREATE FUNCTION ssfnGetStudenytId
(
    -- Add the parameters for the function here
)
RETURNS int
AS
BEGIN

declare @vId as int 
set @vId =  Select stm_studentid  from  sql_studentmarks where stm_mark = (SELECT  MAX( stm_mark )from sql_studentmarks )

RETURN @vId
END