SQL Server - XQuery: delete parent node based on child value substring - sql-server

Question

I want to delete all parent nodes TxDtls of the following XML where position 20 of child value Ref is 2.
<Document xmlns="urn:iso:std:iso:20022:tech:xsd:camt.054.001.04" xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance" xsi:schemaLocation="urn:iso:std:iso:20022:tech:xsd:camt.054.001.04 camt.054.001.04.xsd">
<BkToCstmrDbtCdtNtfctn>
<Ntfctn>
<Ntry>
<TtlChrgsAndTaxAmt Ccy="CHF">1.60</TtlChrgsAndTaxAmt>
<Rcrd>
<Amt Ccy="CHF">1.60</Amt>
<CdtDbtInd>DBIT</CdtDbtInd>
<ChrgInclInd>false</ChrgInclInd>
<Tp>
<Prtry>
<Id>2</Id>
</Prtry>
</Tp>
</Rcrd>
</Chrgs>
<NtryDtls>
<TxDtls>
<RmtInf>
<Strd>
<CdtrRefInf>
<Ref>111118144400000000020076766</Ref>
</CdtrRefInf>
</Strd>
</RmtInf>
</TxDtls>
<TxDtls>
<RmtInf>
<Strd>
<CdtrRefInf>
<Ref>111117645600000000030076281</Ref>
</CdtrRefInf>
</Strd>
</RmtInf>
</TxDtls>
</NtryDtls>
</Ntry>
</Ntfctn>
</BkToCstmrDbtCdtNtfctn>
</Document>
So I want to delete the first TxDtls node (substring position 20 = 2) while I want to keep the second one (substring position 20 <> 2).
I tried this:
UPDATE mytable SET XMLData.modify('delete .//TxDtls[RmtInf/Strd/CdtrRefInf/Ref/substring(text(),20,1) = ''2'']')
However, I get the error "The XQuery syntax '/function()' is not supported". Any hints on how to achieve this?
Thanks

Answer 1

What a difference made by the partially provided minimal reproducible example.
The XML is still not well-formed. I had to comment out the following tag: </Chrgs>
A default namespace is easily handled by its declaration in the XQuery method.
SQL
-- DDL and sample data population, start
DECLARE #tbl TABLE (ID INT IDENTITY PRIMARY KEY, xmldata XML);
INSERT INTO #tbl (xmldata) VALUES
(N'<?xml version="1.0"?>
<Document xmlns="urn:iso:std:iso:20022:tech:xsd:camt.054.001.04"
xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
xsi:schemaLocation="urn:iso:std:iso:20022:tech:xsd:camt.054.001.04 camt.054.001.04.xsd">
<BkToCstmrDbtCdtNtfctn>
<Ntfctn>
<Ntry>
<TtlChrgsAndTaxAmt Ccy="CHF">1.60</TtlChrgsAndTaxAmt>
<Rcrd>
<Amt Ccy="CHF">1.60</Amt>
<CdtDbtInd>DBIT</CdtDbtInd>
<ChrgInclInd>false</ChrgInclInd>
<Tp>
<Prtry>
<Id>2</Id>
</Prtry>
</Tp>
</Rcrd>
<!--</Chrgs>-->
<NtryDtls>
<TxDtls>
<RmtInf>
<Strd>
<CdtrRefInf>
<Ref>111118144400000000020076766</Ref>
</CdtrRefInf>
</Strd>
</RmtInf>
</TxDtls>
<TxDtls>
<RmtInf>
<Strd>
<CdtrRefInf>
<Ref>111117645600000000030076281</Ref>
</CdtrRefInf>
</Strd>
</RmtInf>
</TxDtls>
</NtryDtls>
</Ntry>
</Ntfctn>
</BkToCstmrDbtCdtNtfctn>
</Document>');
-- DDL and sample data population, end
-- before
SELECT * FROM #tbl;
UPDATE #tbl SET xmldata.modify('declare default element namespace "urn:iso:std:iso:20022:tech:xsd:camt.054.001.04";
delete /Document/BkToCstmrDbtCdtNtfctn/Ntfctn/Ntry/NtryDtls/TxDtls[RmtInf/Strd/CdtrRefInf/Ref[substring(./text()[1],20,1) = "2"]]');
-- after
SELECT * FROM #tbl;