Creating An Inline Table-Valued Function In SQL Server

Jeanne Combrinck looks at inline table-valued functions in SQL Server:

Lets start off with what is a table-valued function (TVF)? A TVF is a dynamic table produced at the time of execution, depending on parameters. Like a view, a TVF creates a result set only when it’s executed, but, unlike a view, it can be parameterized.

You get two types of TVFs, an Inline Table-Valued Function (ITVFs) and Multi-statement Table-Valued Function (MTVFs). I find them easy to remember, think of the “I” in ITVF as 1 (single statement) and the “M” in MTVF as “many” (multiple statements).

As you can imagine, a TVF produces a result set that can be used as a virtual table or view. Yes, you can actually select data from a TVF, or join it with some other tables, views, or even other TVFs. In this post I will go into more detail on ITVFs.

In my experience, the best part about using inline table-valued function is the 3-9x performance improvement you get when removing them and inlining their code.  It’s a great idea but the performance cost is just too high for me.

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