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Strange behaviour


Strange behaviour

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schleep
schleep
Mr or Mrs. 500
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FWIW, Thinking it might have been generating an n x 1 CROSS JOIN, I moved the JOIN dbo.lookup out of the select statement in the function, since it wasn't actually JOINing the other tables. This had no effect.



schleep
schleep
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So it turns out that in the 2 failing scenarios, the function is going through the full table before applying the WHERE clause, and failing on a row where first name or last name is null.

In the working scenarios, the WHERE clause is applied first, and only one row is acted on.

So am I to conclude that order does matter in the FROM clause?



ChrisM@Work
ChrisM@Work
SSCrazy Eights
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schleep (7/9/2014)
So it turns out that in the 2 failing scenarios, the function is going through the full table before applying the WHERE clause, and failing on a row where first name or last name is null.

In the working scenarios, the WHERE clause is applied first, and only one row is acted on.

So am I to conclude that order does matter in the FROM clause?

The execution plans for the working queries and the non-working queries are obviously different. You can't really jump to any conclusions without examining them.

“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
ChrisM@Work
ChrisM@Work
SSCrazy Eights
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Group: General Forum Members
Points: 8921 Visits: 19004
-- You might want to configure that function as an iTVF for performance:
CREATE FUNCTION [dbo].[iTVF_CallbackService_ufn_GetCallerData]
(
   @nCaller_NoArg   INTEGER,
   @cCallerLangArg   CHAR(1)
)

RETURNS TABLE
AS
RETURN (

   SELECT   
      [Caller_No]            = @nCaller_NoArg,
      [Clientname]         = RTRIM(LTRIM(c.First_Name)) + ' ' + RTRIM(LTRIM(c.Last_Name)),
      [ClientLanguage]      = CASE   
                  WHEN @cCallerLangArg = 'F'
                  THEN UPPER(RTRIM(LTRIM(l.Descript_f)))
                  ELSE UPPER(RTRIM(LTRIM(l.Descript)))
                  END,
      [ClientOrganization]   = ISNULL(RTRIM(LTRIM(c.Organization)), ''),
      [ClientAddressLine1]   = ISNULL(RTRIM(LTRIM(c.Street)), ''),

      [ClientAddressLine2]   = ISNULL(RTRIM(LTRIM(c.City)) + ', ' + CASE   
                  WHEN @cCallerLangArg = 'F'
                  THEN UPPER(RTRIM(LTRIM(c.ps_prov_code))) -- c.ps_prov_code_f???
                  ELSE UPPER(RTRIM(LTRIM(c.ps_prov_code)))
                  END + ' ' +
         RTRIM(LTRIM(CASE   
                  WHEN c.Postcode LIKE '[A-Z][0-9][A-Z][0-9][A-Z][0-9]'
                  THEN LEFT(c.PostCode, 3) + ' ' + RIGHT(c.PostCode, 3)
                  ELSE c.PostCode
                  END)), ''),

      [ClientAddressLine3]   = ISNULL(CASE   
                  WHEN @cCallerLangArg = 'F'
                  THEN UPPER(RTRIM(LTRIM(s_country_name_f)))
                  ELSE UPPER(RTRIM(LTRIM(s_country_name)))
                  END, ''),

      [ClientTelephone1]      = ISNULL(RTRIM(LTRIM(c.Telephone)), ''),
      [ClientTelephone1Ext]   = ISNULL(RTRIM(LTRIM(c.Extension)), ''),
      [ClientTelephone2]      = ISNULL(RTRIM(LTRIM(c.Night_Phone)), ''),
      [ClientTelephone2Ext]   = '',
      [ClientEmail]         = ISNULL(RTRIM(LTRIM(c.s_Email)), '')

   FROM dbo.[Caller] c
   CROSS JOIN dbo.[Lookup] l   
      
   LEFT OUTER JOIN   dbo.Province p   
      ON p.ps_Prov_Code = c.ps_Prov_Code

   LEFT OUTER JOIN   dbo.Country   ct   
      ON ct.ps_country_code = c.Country

   WHERE c.Caller_No = @nCaller_NoArg
      AND l.lookup_ch = @cCallerLangArg
      AND l.Item_name = 'Language'

)



“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
schleep
schleep
Mr or Mrs. 500
Mr or Mrs. 500 (514 reputation)Mr or Mrs. 500 (514 reputation)Mr or Mrs. 500 (514 reputation)Mr or Mrs. 500 (514 reputation)Mr or Mrs. 500 (514 reputation)Mr or Mrs. 500 (514 reputation)Mr or Mrs. 500 (514 reputation)Mr or Mrs. 500 (514 reputation)

Group: General Forum Members
Points: 514 Visits: 1286
Hi Chris,

Yep, that was my conclusion too. However, since query fails, I couldn't see the execution plan. Unless there's a way?

And, the iTVF would probably neatly obviate the original NULL value problem, too!

Thanks!



ChrisM@Work
ChrisM@Work
SSCrazy Eights
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Group: General Forum Members
Points: 8921 Visits: 19004
The query was failing because one or more columns in the original multi-statement table-valued function were non-nullable. It's unlikely that changing the nullability of those columns would change the plan.

“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
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