XQuery插入/更新值

Question

I want to update xml like this one

<?xml version="1.0" encoding="utf-16"?>
<Properties xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance" xmlns:xsd="http://www.w3.org/2001/XMLSchema">
 <BackupPath>MyLocalPath</BackupPath>
</Properties>

using stored procedure

declare @PropertyName       nvarchar(500)
declare @PropertyValue      nvarchar(MAX)

set @PropertyName = 'BackupPath'
set @PropertyValue = 'MyTestPath'

DECLARE @ExistingSettings XML;
DECLARE @NewSettings nvarchar(MAX);

SET @ExistingSettings = (SELECT TOP(1) CAST(SettingsDefinition  AS XML) FROM ApplicationSettings)

SET @ExistingSettings.modify('replace value of (/Properties/*[local-name() = sql:variable("@PropertyName")]/text())[1] with sql:variable("@PropertyValue")')

UPDATE ApplicationSettings
SET SettingsDefinition = CAST(@ExistingSettings AS nvarchar(MAX)), LastUpdate = GetDate()
WHERE ID = (SELECT TOP(1) ID FROM ApplicationSettings)

and this works fine as long as 'BackupPath' contains value

<BackupPath>MyLocalPath</BackupPath>

How to modify this query to insert value (or validate if needed) if

<BackupPath />

Answer 1

Just don't require a text node in your XPath.

SET @ExistingSettings.modify(
  'replace value of (/Properties/' + @PropertyName + ')[1] with sql:variable("@PropertyValue")'
)