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UDF Help


UDF Help

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rocky_498
rocky_498
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Hi Guys,

I want to create UDF. Below is my logic. Please guide me where i am wrong.


Alter Function [dbo].[udf_GPList](@EID int,@PID int)




returns varchar(1000)
as

begin
Declare @Pist varchar(1000)=''
Declare @OID as varchar(2000) = ''
Declare @OTID as varchar(2000) = ''

SELECT
@OID = O.OId,
@OTID = O.OTId
From dbo.Order O
INNER JOIN dbo.PList PL ON PL.PId = O.PId
INNER JOIN dbo.Ens E ON E.EId = O.EId
WHERE PL.PId = @PID
AND E.EId = @Eid


SELECT
@Pist =
dbo.udfOrGetDetail (@OID,@OTID) +'<br />'
FROM dbo.PList TPL
INNER JOIN dbo.Ens E ON E.PId = TPL.PId
INNER JOIN dbo.Order O ON O.EId = E.EId
WHERE
E.EId = @EID
AND TPL.PId = @PID



Set @Pist= ISNULL(@Pist,'')

RETURN @Pist


END

Thanks in advance. If i am understand right. Function can return only one value. am i right?
Lynn Pettis
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I'm not even sure what you are trying to accomplish. Plus, what is the other function doing? There really isn't enough information to really provide much help.

You may want to read the first article I reference below in my signature block regarding asking for help. Follow the instructions in that article regarding what yu need to post and how to post it to get the best answers.

Cool
Lynn Pettis

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What is the problem you are facing when you create the UDF?
Alan.B
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If i am understand right. Function can return only one value. am i right?


Scalar functions return one value, table valued functions return a table variable.

-- Alan Burstein



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Alan.B (2/25/2013)

If i am understand right. Function can return only one value. am i right?


Scalar functions return one value, table valued functions return a table variable.


Inline Table Valued Functions (iTVF for short) return a result set even if that result set is a single element. Think of it as an Inline Scalar Function. The "inline" type of function is about 7 times faster than any scalar function and also works faster for MultiLine Table Valued Fuctions.

--Jeff Moden

RBAR is pronounced ree-bar and is a Modenism for Row-By-Agonizing-Row.
First step towards the paradigm shift of writing Set Based code:
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TheSQLGuru
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You may THINK you want to do a Scalar UDF, but you probably don't. I wrote a chapter for the SQL Server MVP Deep Dives 2 book entitled "Death by UDF". It is a very aptly named missive. Please do everything in your power to avoid the UDF and inline the code where you need it.

Oh, I haven't tested it, but I wonder if UDFs can call UDFs ...

Best,
Kevin G. Boles
SQL Server Consultant
SQL MVP 2007-2012
TheSQLGuru on googles mail service
ChrisM@Work
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The second query is a red herring. It will do this:

SELECT @Pist = dbo.udfOrGetDetail (@OID,@OTID) +'<br />'

as many times as rows returned by everything after the FROM list. Each time it runs it will generate exactly the same result, and then it will throw away all except the last result. As Kevin has pointed out, there is some scope for performance improvement here.

“Write the query the simplest way. If through testing it becomes clear that the performance is inadequate, consider alternative query forms.” - Gail Shaw

For fast, accurate and documented assistance in answering your questions, please read this article.
Understanding and using APPLY, (I) and (II) Paul White
Hidden RBAR: Triangular Joins / The "Numbers" or "Tally" Table: What it is and how it replaces a loop Jeff Moden
Exploring Recursive CTEs by Example Dwain Camps
Jeff Moden
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TheSQLGuru (2/27/2013)
You may THINK you want to do a Scalar UDF, but you probably don't. I wrote a chapter for the SQL Server MVP Deep Dives 2 book entitled "Death by UDF". It is a very aptly named missive. Please do everything in your power to avoid the UDF and inline the code where you need it.

Oh, I haven't tested it, but I wonder if UDFs can call UDFs ...


Yes they can. if they're not iTVFs, it about as joyous as an aggregated view calling an aggregated view.

--Jeff Moden

RBAR is pronounced ree-bar and is a Modenism for Row-By-Agonizing-Row.
First step towards the paradigm shift of writing Set Based code:
Stop thinking about what you want to do to a row... think, instead, of what you want to do to a column.
If you think its expensive to hire a professional to do the job, wait until you hire an amateur. -- Red Adair

Helpful Links:
How to post code problems
How to post performance problems
Forum FAQs
ChrisM@Work
ChrisM@Work
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Group: General Forum Members
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Jeff Moden (2/27/2013)
TheSQLGuru (2/27/2013)
You may THINK you want to do a Scalar UDF, but you probably don't. I wrote a chapter for the SQL Server MVP Deep Dives 2 book entitled "Death by UDF". It is a very aptly named missive. Please do everything in your power to avoid the UDF and inline the code where you need it.

Oh, I haven't tested it, but I wonder if UDFs can call UDFs ...


Yes they can. if they're not iTVFs, it about as joyous as an aggregated view calling an aggregated view.


Which could get very aggregating.

“Write the query the simplest way. If through testing it becomes clear that the performance is inadequate, consider alternative query forms.” - Gail Shaw

For fast, accurate and documented assistance in answering your questions, please read this article.
Understanding and using APPLY, (I) and (II) Paul White
Hidden RBAR: Triangular Joins / The "Numbers" or "Tally" Table: What it is and how it replaces a loop Jeff Moden
Exploring Recursive CTEs by Example Dwain Camps
TheSQLGuru
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. . .it about as joyous as an aggregated view calling an aggregated view.


You can do THAT TOO in SQL Server?!? Jeez, what a suck-@ss product! w00t

Best,
Kevin G. Boles
SQL Server Consultant
SQL MVP 2007-2012
TheSQLGuru on googles mail service
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