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title Logical Expressions (XQuery) | Microsoft Docs
ms.custom
ms.date 03/14/2017
ms.prod sql
ms.prod_service sql
ms.reviewer
ms.technology xml
ms.topic language-reference
dev_langs
XML
helpviewer_keywords
logical operators [SQL Server], XQuery
effective Boolean value [XQuery]
logical expressions [XQuery]
EBV
expressions [XQuery], logical
ms.assetid de94cd2e-2d48-49fb-9ebd-a2d90c79bf62
author rothja
ms.author jroth

Logical Expressions (XQuery)

[!INCLUDEtsql-appliesto-ss2012-xxxx-xxxx-xxx-md]

XQuery supports the logical and and or operators.

expression1 and expression2  
expression1 or expression2

The test expressions, expression1,``expression2, in [!INCLUDEssNoVersion] can result in an empty sequence, a sequence of one or more nodes, or a single Boolean value. Based on the result, their effective Boolean value is determined in the following manner:

  • If the test expression results in an empty sequence, the result of the expression is False.

  • If the test expression results in a single Boolean value, this value is the result of the expression.

  • If the test expression results in a sequence of one or more nodes, the result of the expression is True.

  • Otherwise, a static error is raised.

The logical and and or operator is then applied to the resulting Boolean values of the expressions with the standard logical semantics.

The following query retrieves from the product catalog the front-angle small pictures, the <Picture> element, for a specific product model. Note that for each product description document, the catalog can store one or more product pictures with different attributes, such as size and angle.

SELECT CatalogDescription.query('  
     declare namespace PD="https://schemas.microsoft.com/sqlserver/2004/07/adventure-works/ProductModelDescription";  
     for $F in /PD:ProductDescription/PD:Picture[PD:Size="small"   
                                                 and PD:Angle="front"]  
     return   
         $F   
    ') as Result  
FROM  Production.ProductModel  
where ProductModelID=19

This is the result:

<PD:Picture   
  xmlns:PD="https://schemas.microsoft.com/sqlserver/2004/07/adventure-works/ProductModelDescription">  
  <PD:Angle>front</PD:Angle>  
  <PD:Size>small</PD:Size>  
  <PD:ProductPhotoID>31</PD:ProductPhotoID>  
</PD:Picture>

See Also

XQuery Expressions