functions-on-sequences-empty.md

title	empty Function (XQuery) | Microsoft Docs
ms.custom
ms.date	03/09/2017
ms.prod	sql
ms.prod_service	sql
ms.reviewer
ms.technology	xml
ms.topic	language-reference
dev_langs	XML
helpviewer_keywords	empty function fn:empty function
ms.assetid	46da89a8-0cd9-4913-8521-4087589a04ba
author	rothja
ms.author	jroth

Functions on Sequences - empty

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

Returns True if the value of $arg is an empty sequence. Otherwise, the function returns False.

Syntax

  
fn:empty($arg as item()*) as xs:boolean  

Arguments

$arg
A sequence of items. If the sequence is empty, the function returns True. Otherwise, the function returns False.

Remarks

The fn:exists() function is not supported. As an alternative, the not() function can be used.

Examples

This topic provides XQuery examples against XML instances that are stored in various xml type columns in the AdventureWorks database.

A. Using the empty() XQuery function to determine if an attribute is present

In the manufacturing process for Product Model 7, this query returns all the work center locations that do not have a MachineHours attribute.

SELECT ProductModelID, Instructions.query('  
declare namespace AWMI="https://schemas.microsoft.com/sqlserver/2004/07/adventure-works/ProductModelManuInstructions";  
     for $i in /AWMI:root/AWMI:Location[empty(@MachineHours)]  
     return  
       <Location  
            LocationID="{ ($i/@LocationID) }"  
            LaborHrs="{ ($i/@LaborHours) }" >  
            {   
              $i/@MachineHours  
            }    
       </Location>  
') as Result  
FROM Production.ProductModel  
where ProductModelID=7  

This is the result:

ProductModelID      Result          
-------------- ------------------------------------------  
7              <Location LocationID="30" LaborHrs="1"/>  
               <Location LocationID="50" LaborHrs="3"/>  
               <Location LocationID="60" LaborHrs="4"/>  

The following, slightly modified, query returns "NotFound" if the MachineHour attribute is not present:

SELECT ProductModelID, Instructions.query('  
declare namespace p14="https://schemas.microsoft.com/sqlserver/2004/07/adventure-works/ProductModelManuInstructions";  
     for $i in /p14:root/p14:Location  
     return  
       <Location  
            LocationID="{ ($i/@LocationID) }"  
            LaborHrs="{ ($i/@LaborHours) }" >  
            {   
                 if (empty($i/@MachineHours)) then  
                    attribute MachineHours { "NotFound" }  
                 else  
                    attribute MachineHours { data($i/@MachineHours) }  
            }    
       </Location>  
') as Result  
FROM Production.ProductModel  
where ProductModelID=7  

This is the result:

ProductModelID Result                         
-------------- -----------------------------------  
7                
  <Location LocationID="10" LaborHrs="2.5" MachineHours="3"/>  
  <Location LocationID="20" LaborHrs="1.75" MachineHours="2"/>  
  <Location LocationID="30" LaborHrs="1" MachineHours="NotFound"/>  
  <Location LocationID="45" LaborHrs="0.5" MachineHours="0.65"/>  
  <Location LocationID="50" LaborHrs="3" MachineHours="NotFound"/>  
  <Location LocationID="60" LaborHrs="4" MachineHours="NotFound"/>  

See Also

XQuery Functions against the xml Data Type
exist() Method (xml Data Type)