Performance of Inline-TVF vs. Views I have a database where i am using inline TVFs (table value functions) instead of views.  For example, I might have two tables called [car model] and [car manufacturer] that I'm joining together inside the TVF [fnCarBrands].  

These TVFs are then called by other TVFs to do further processing and reporting.  So I might take my function [fnCarBrands] and join to the table [Purchase Year] to form a function [fnCarBrandHistory].  And so on for several layers of TVFs.  

I could probably get the same functionality using views, since my inline TVFs are really just joins of tables and other TVFs.  

How does the performance of inline TVFs written in this way compare with views?
The query optimizer treats an inline table valued function exactly like a view:

CREATE FUNCTION dbo.InlineUdf(@arg1 int)
RETURNS TABLE
AS
RETURN 
(
    ... your query here ...
);


A multi-statement table-valued function is run more like a stored procedure.  They typically have to be executed multiple times, rather than be folded into the main query:

CREATE FUNCTION dbo.MultiStatementUdf (@col1 int)
RETURNS @result TABLE 
(
    id int primary key NOT NULL,
    ... 
)
AS
BEGIN
   DECLARE @var1 int
   set @var1 = 42

   INSERT @result
   SELECT ...
   RETURN
END;