Is there any performance differences between function type IF and TF?

I could not found more references in BOA about functions that return table.
Does anybody know if there is any performance differences between these two
type of functions?
IF = Inlined table-function
TF = Table function
Thanks,
LijunLijun Zhang (nospam@.nospam.nospam) writes:
> I could not found more references in BOA about functions that return
> table. Does anybody know if there is any performance differences between
> these two type of functions?
> IF = Inlined table-function
> TF = Table function
Yes, there is.
An inline function is in fact not a function at all; it is a macro. The
optimiser pastes the text of the function into the query and optimizes
the result.
A multi-step function returns data to a table variable, and the result
of the function is opaque to the optimizer.
Thus, in the former case the optimizer have more information, and
thus better possibilities to create a better execution plan.
But sometimes it can be too much information, so in fact it leads
to poorer performance. But in the long run, inline functions will
give you better performance.
--
Erland Sommarskog, SQL Server MVP, esquel@.sommarskog.se
Books Online for SQL Server SP3 at
http://www.microsoft.com/sql/techin.../2000/books.asp|||Yes, there may be a significant difference, although of course that
depends on exactly what you are doing.
Despite the similar syntax *inline* table-valued functions are
implemented very differently from *multi-statement* table-valued
functions.
A inline table-valued function consists of a single query that works
very like a view. That is, when the function is referenced in another
query the SQL from both the calling query and the function itself is
considered together so as to arrive at an optimal execution plan.
With a multi-statement table-valued function that kind of optimization
isn't possible. In a multi-statement function the function code is
executed more like a stored procedure and then a result returned to the
calling code for further processing.
If you want to encapsulate a single query in a function then use an
inline TVF, or use a view.
If you need to put multiple statements in a function then you'll have
to use a multi-statement TVF.
David Portas
SQL Server MVP
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