Incorrect syntax near 'BEGIN'. in TSQL - sql-server

Question

hello programmers i'm writing a TSQL in-line table function, actually im not good enough in sql, when i finished my code i've got this error "Incorrect syntax near 'BEGIN'." , anyone know the solution please give it to me.
by the way when i clicked double-click over the error msg it's selected the last "end"
create FUNCTION [dbo].[CheckLogin]
(
#un varchar(max),
#pw varchar(max)
)
RETURNS TABLE
AS
begin
declare #unexist int, #unpwmatch int, #uid bigint
declare #uisactivated bit , #uisdeleted bit
-----
set #unexist = (select COUNT(UserAccessInfo.UserId) FROM UsersAccessInfo
WHERE UserAccessInfo.UserName = #un OR UserAccessInfo.UserEmail = #un)
------
set #unpwmatch = (select count(usersaccessinfo.userid) from usersaccesinfo
WHERE (usersaccessinfo.UserName = #un) AND (usersaccessinfo.UserPassword = #pw) OR
(usersaccessinfo.UserEmail = #un) AND (usersaccessinfo.UserPassword = #pw))
------
set #uid =(select usersaccessinfo.userid from usersaccessinfo where
serAccessInfo.UserName = #un OR UserAccessInfo.UserEmail = #un)
------
if #uid <> Null
begin
set #uisactivated =(select usersaccessinfo.userisactivated from usersaccessinfo
where usersaccessinfo.userid=#uid)
end
------
if #uid <> null
begin
set #uisactivated =(select usersaccessinfo.userisactivated from usersaccessinfo
where usersaccessinfo.userid=#uid)
end
------
if #unexist = 0
begin
select dbo.getreportbyid('1004')
end;
else if #unpwmatch = 0
begin
select dbo.getreportbyid('1005')
end;
else if #uid<>0
begin
if #uisactivated =0
begin
select dbo.getreportbyid('1002')
end;
else if #uisdeleted = 1
begin
select dbo.getreportbyid('1003')
end;
end;
else
begin
select ('successful') as report
end;
return
end;

Answer 1

The problem is these lines:
...
RETURNS TABLE
AS
...
This is not valid syntax for any of the four types of user-defined functions.
Assuming that you are trying to define a multi-statement table-valued function, it should look like this:
...
RETURNS #YourTableName TABLE( <column-definitions>... )
AS
...
And then your function statements should be putting the function return data into that table before it executes the RETURN statement, which it also is not doing.

Answer 2

Your problem is that you are mixing the syntax of multi-statement table valued functions and inline table valued functions. For examples of each and some performance considerations check out my post here: http://sqlity.net/en/498/t-sql-tuesday-24-prox-n-funx/
In short, if you want to use multiple statements within a table valued function you have to declare a table variable after the RETURNS keyword and insert the rows you want to return in there in the function body. However, this type of function has serious performance implications and you should try hard to stay away from it.
Besides of that, you seem to have mismatching BEGINs and ENDs. As Barry said, "A little indentation would go a long way here" in helping you and others understand you code better.

Answer 3

You cannot have ; before the if command end. Also null checing is wrong. For ex;
if #uid <> null -- (1) note: should be if #uid is not null
Begin
-- query
End; --(2)-Note: this is wrong
Else
Begin
--Query
End