Clear documentation in regards to User-defined functions restrictions

Question

I've been searching online for a clear list of restrictions in User-defined functions and the best I found so far is

http://technet.microsoft.com/en-us/library/ms191320.aspx

I found good blog by Pinal Dave, but I'm looking for official MS documentation.

Thanks in advance.

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Answer 1

Hi,

I find the following link provides specific guidelines, rules and restrictions.Please see:
User-Defined Function Design Guidelines
http://msdn.microsoft.com/en-us/library/ms187440.aspx

Thanks,
Ai-hua Qiu

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Ai-hua Qiu[MSFT]
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Answer 2

Hi Ai-hua,

Unless for me this link returns different info, I don't see a clear list of things which are not allowed in a function. I believe I checked that link above before.

I need something very similar to Pinal's blog

http://blog.sqlauthority.com/2007/05/29/sql-server-user-defined-functions-udf-limitations/

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Answer 3

Most important thing to remember:

You cannot change the database in any shape or form within a UDF.

READ-ONLY access to the databases within a function.

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Kalman Toth SQL SERVER 2012 & BI TRAINING
New Book: Beginner Database Design & SQL Programming Using Microsoft SQL Server 2012

Answer 4

Yes, that I know. I just thought there should be an explicit list of things that are not allowed in a function. Say, Pinal's blog mentions that UDF can not return XML. Recently there was a thread on this topic and that's why I started to look for clear documentation. So far I found none in BOL.

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Answer 5

Hello Naomi,

What about this link ?

http://www.databasejournal.com/features/mssql/article.php/3904491/Creating-User-Defined-Functions-in-Microsoft-SQL-Server.htm

You are true : it is really difficult to find complete information about the restrictions about user-defined functions in MS documentation

Have a nice day

PS : i discovered this link ( a little old one ) :

http://decipherinfosys.wordpress.com/2008/07/16/udf-limitations-in-sql-server/

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Answer 6

Thanks, Papy. The second link is good, but I don't think it lists everything. And also, it's not BOL documentation.

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