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PODoes using nullif() statements with xquery in SQL Server ruin xquery optimization?
 

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  1. PODoes using nullif() statements with xquery in SQL Server ruin xquery optimization?
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    <p>I have the following block of dynamic SQL in SQL Server 2008 (as part of a larger query):</p> <pre><code>insert into '+@schema+'.HP_Payers (HeadingID, PayerName, PayerID_Qualifier, PayerID, Address1, Address2, City, StateCode, ZipCode) select @headingID as HeadingID, nullif(c.value(''Name'', ''varchar(60)''), '''') as PayerName, nullif(c.value(''ID_Qualifier'', ''varchar(2)''), '''') as PayerID_Qualifier, nullif(c.value(''ID_Code'', ''varchar(80)''), '''') as PayerID, nullif(c.value(''Address1'', ''varchar(55)''), '''') as Address1, nullif(c.value(''Address2'', ''varchar(55)''), '''') as Address2, nullif(c.value(''City'', ''varchar(30)''), '''') as City, nullif(c.value(''StateCode'', ''char(2)''), '''') as StateCode, nullif(c.value(''ZipCode'', ''varchar(15)''), '''') as ZipCode from '+@schema+'.IntegrationQueue cross apply InputValue.nodes(''/ROOT/Payer'') t(c) where QueueID = @queueID </code></pre> <p>which inserts the correct data from the given node in the 'from' statement into a new table. The entire query itself ran a set of 10 XML files about 10 seconds faster than it did before I added the nullif() statements. I also found this tidbit of info on MS documentation regarding xquery optimization:</p> <p><em>The value() method calls must appear contiguously in a SELECT list to be merged. The execution of non-contiguous value() methods are not combined.</em></p> <p>So my question is does placing these nullif() statements essentially ruin this performance gain described here? Any help would be appreciated.</p>
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