How to update empty XML node in MSSQL - sql-server

Question

I want to update empty XML variable in MSSQL
i try every solutions like replace, outer apply , modify but nothing working
please help me find a solutions
<ArrayOfField xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance" xmlns:xsd="http://www.w3.org/2001/XMLSchema">
<Field>
<FieldType>1</FieldType>
<DataType>1</DataType>
<Label>department</Label>
<Name>department</Name>
<Description />
<Min />
<Max />
<DefaultValue />
<Required>0</Required>
<SelectItems />
<Formula />
<DataSourceUID xsi:nil="true" />
<TrueText />
<FalseText />
<UnconfirmtyRule xsi:nil="true" />
<UnconfirmtyRequired xsi:nil="true" />
<UnconfirmityFormUID xsi:nil="true" />
<ConfirmationStatus xsi:nil="true" />
<ConfirmationUserBasedType xsi:nil="true" />
<ConfirmationRightUsers />
<Newline>false</Newline>
<ColumnWith>12</ColumnWith>
<Offset>0</Offset>
</Field>
<Field>
<FieldType>1</FieldType>
<DataType>4</DataType>
<Label>Test</Label>
<Name>test</Name>
<Description />
<Min />
<Max />
<DefaultValue />
<Required>0</Required>
<SelectItems />
<Formula />
<TrueText />
<FalseText />
<UnconfirmtyRule xsi:nil="true" />
<UnconfirmtyRequired xsi:nil="true" />
<UnconfirmityFormUID xsi:nil="true" />
<ConfirmationStatus xsi:nil="true" />
<ConfirmationUserBasedType xsi:nil="true" />
<ConfirmationRightUsers />
<Newline>false</Newline>
<ColumnWith>12</ColumnWith>
<Offset>0</Offset>
</Field>
</ArrayOfField>
I want update DefaultValue if DataType = 1
New DefaultValue like <DefaultValue>TODAY()<DefaultValue/>
I try this code but not update anything what is my mistake?
DECLARE #SearchType NVARCHAR(100)=N'1';
DECLARE #ReplaceWith NVARCHAR(100)=N'TODAY()';
UPDATE FormSchema
SET Fields.modify('replace value of
(/ArrayOfField
/Field[DataType=sql:variable("#SearchType")]
/DefaultValue/text())[1]
with sql:variable("#ReplaceWith")')
WHERE Fields.exist('/ArrayOfField
/Field[DataType=sql:variable("#SearchType")]')=1;

Answer 1

You need to use different XML modify operations depending on whether the target element is empty or not (i.e.: it contains no text as opposed to being xsi:nil="true"). For example...
--
-- Setup data...
--
create table dbo.FormSchema (
Fields xml
);
insert dbo.FormSchema (Fields) values
(N'<ArrayOfField>
<Field>
<DataType>1</DataType>
<DefaultValue>Hello, world!</DefaultValue>
</Field>
<Field>
<DataType>2</DataType>
<DefaultValue />
</Field>
</ArrayOfField>'),
(N'<ArrayOfField>
<Field>
<DataType>1</DataType>
<DefaultValue />
</Field>
<Field>
<DataType>3</DataType>
<DefaultValue />
</Field>
</ArrayOfField>');
--
-- Perform updates...
--
DECLARE
#SearchType NVARCHAR(100) = N'1',
#ReplaceWith NVARCHAR(100) = N'TODAY()';
UPDATE dbo.FormSchema
SET Fields.modify('
replace value of (/ArrayOfField/Field[DataType=sql:variable("#SearchType")]/DefaultValue/text())[1]
with sql:variable("#ReplaceWith")
')
WHERE Fields.exist('(/ArrayOfField/Field[DataType=sql:variable("#SearchType")]/DefaultValue/text())[1]')=1;
UPDATE dbo.FormSchema
SET Fields.modify('
insert text{sql:variable("#ReplaceWith")}
into (/ArrayOfField/Field[DataType=sql:variable("#SearchType")]/DefaultValue)[1]
')
WHERE Fields.exist('(/ArrayOfField/Field[DataType=sql:variable("#SearchType")]/DefaultValue)[1]')=1
AND Fields.exist('(/ArrayOfField/Field[DataType=sql:variable("#SearchType")]/DefaultValue/text())[1]')=0;
--
-- Check results...
--
SELECT * FROM dbo.FormSchema;
Which yields the results:
Fields
<ArrayOfField><Field><DataType>1</DataType><DefaultValue>TODAY()</DefaultValue></Field><Field><DataType>2</DataType><DefaultValue /></Field></ArrayOfField>
<ArrayOfField><Field><DataType>1</DataType><DefaultValue>TODAY()</DefaultValue></Field><Field><DataType>3</DataType><DefaultValue /></Field></ArrayOfField>