Looking for some guidance on avoiding Scalar UDFs for DB lookups

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Looking for some guidance on avoiding Scalar UDFs for DB lookups

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ScottPletcher SSC Guru Points: 101098 More actions · Answer 1

You should get rid of the local variable as it's not needed and causes overhead. Also, make sure that ANSI_NULLS and QUOTED_IDENTIFIER are set properly when the function is created.

SET ANSI_NULLS ON;
SET QUOTED_IDENTIFIER ON;
GO
CREATE FUNCTION [dbo].[F_ISWOSTATUSWAITPOSSIBLE] (
    @WO_Status char(2)
)
RETURNS bit
AS
BEGIN
RETURN (
    CASE WHEN @WO_Status in ('30', '40', '50', '60', '65', '70') THEN CAST(1 AS bit) ELSE CAST(0 AS bit) END
)
END

SQL DBA,SQL Server MVP(07, 08, 09) "It's a dog-eat-dog world, and I'm wearing Milk-Bone underwear." "Norm", on "Cheers". Also from "Cheers", from "Carla": "You need to know 3 things about Tortelli men: Tortelli men draw women like flies; Tortelli men treat women like flies; Tortelli men's brains are in their flies".

Johan Bijnens SSC Guru Points: 135369 More actions · Answer 2

Indeed, but best is to just avoid the SVF

This reply was modified 2 years, 5 months ago by Johan Bijnens.

Johan

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Jeff Moden SSC Guru Points: 1004340 More actions · Answer 3

Sorry... not enough coffee yet. Misread some code and removed the post.

And I totally agree with Johan... avoid Scalar UDFs at all costs. They even prevent parallelism if you do a select from a table if you have one in a computed column even if you don't use the computed column. Brent Ozar wrote about that and I've verified his findings.

--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.

Change is inevitable... Change for the better is not.

Helpful Links:
How to post code problems
How to Post Performance Problems
Create a Tally Function (fnTally)

SwePeso SSC-Dedicated Points: 39757 More actions · Answer 4

Something like this?

        WITH cteAggregated(CustomerID, ItemID, Yak)
        AS (
                SELECT          CustomerID,
                                ItemID,
                                MIN(CAST(MyLevelHere AS VARBINARY(1)) + CAST(MyPriceHere AS VARBINARY(MAX)) AS Yak
                FROM            dbo.MyTableNameHere
                GROUP BY        CustomerID,
                                ItemID
        )
        SELECT  CustomerID,
                ItemID,
                CAST(SUBSTRING(Yak, 1, 1) AS VARCHAR(1)) AS MyLevelHere,
                CAST(SUBSTRING(Yak, 2, LEN(Yak) - 1) AS DECIMAL(19, 4)) AS MyPriceHere
        FROM    cteAggregated;

It's hard to say exactly without knowing your DDL.

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SteveOC Ten Centuries Points: 1257 More actions · Answer 5

Thanks all. I managed to get it to do what I needed by breaking down into 3 queries and can run all 3 within 20 seconds. It it was not perfect and required additional outliers to be added so was a WIP. Then the business decided to change the pricing on certain things which kind of broke it - at least requiring the addition of a bunch of exclusions. I will review the responses in more detail as my understanding develops (just starting out using CTEs) and revisit the code when I get a chance.