use tempdb;
go

create function dbo.fnBasic_Scalar
(
 @a int
)
returns int
as
begin
 return @a;
end;
go

create function dbo.fnWrapper1
(
 @a int
)
returns int
as
begin
 return dbo.fnBasic_Scalar(@a);
end;
go

create function dbo.fnBasic_Inline
(
 @a int
)
returns table
as
return (select @a as a);
go

create function dbo.fnWrapper2
(
 @a int
)
returns int
as
begin
 return (select top (1) a from dbo.fnBasic_Inline(@a));
end;
go

create table dbo.t (id int primary key, a1 as dbo.fnWrapper1(id), a2 as dbo.fnWrapper2(id));
go

insert into dbo.t
 (id)
 select top (1000000)
  row_number() over (order by rand())
 from
  master.dbo.spt_values a cross join
  master.dbo.spt_values b
go

declare @a int;

set statistics time on;
select @a = a1 from dbo.t;
select @a = a2 from dbo.t;
set statistics time off;

drop table dbo.t;
drop function dbo.fnWrapper1, dbo.fnWrapper2, dbo.fnBasic_Scalar, dbo.fnBasic_Inline;
go

Время работы SQL Server:
   Время ЦП = 8221 мс, затраченное время = 8380 мс.

 Время работы SQL Server:
   Время ЦП = 5413 мс, затраченное время = 5543 мс.