Question

for a table valued function in sql why cant we write sql statements inside begin and end tags like-

create function dbo.emptable()
returns Table
as
BEGIN --it throws an error
return (select id, name, salary from employee)
END
go

while in scalar valued function we can use these tags like

create function dbo.countemp()
returns int
as
begin
return (select count(*) from employee)
end
go

is there any specific rule where we should use BEGIN & END tags

Answer 1

The multi-statement table-valued
function is slightly more complicated
than the other two types of functions
because it uses multiple statements to
build the table that is returned to
the calling statement. Unlike the
inline table-valued function, a table
variable must be explicitly declared
and defined. The following example
shows how to implement a
multi-statement table-valued function
that populates and returns a table
variable.

USE Northwind
go
CREATE FUNCTION fx_OrdersByDateRangeAndCount
( @OrderDateStart smalldatetime, 
  @OrderDateEnd smalldatetime, 
  @OrderCount smallint )
RETURNS @OrdersByDateRange TABLE
  (  CustomerID nchar(5),
     CompanyName nvarchar(40),
     OrderCount smallint,
     Ranking char(1) )
AS
BEGIN
// statements that does some processing ....

END

From the above, I guess BEGIN and END denotes the intent/use of multiple statements & hence it requires the table variable to be defined as shown in the code above.

from http://www.sqlteam.com/article/intro-to-user-defined-functions-updated