How to extract schema from XML variable using XQuery - sql-server

Question

Technologies: T-SQL, XML, XQuery
I have an XML #variable in a database table which has a schema section and data section. I would only like to extra only the schema section and create a XML Schema Collection for it. It appears XQuery would be the quickest way. How do I specify the starting tag and ending tag in the following file (I only want to extract everything between <xs:schema xmlns and </xs:schema>?
CREATE FUNCTION [etl].[ufn_GetXmlSchema]
(
#DataLakeBlobId uniqueidentifier
)
RETURNS xml
AS
BEGIN
DECLARE #XmlSchema xml
,#XmlData xml
SET #XmlSchema = ( SELECT [XmlData]
FROM [landing].[v_tbForm] WITH (NOLOCK)
WHERE [DataLakeBlobId] = #DataLakeBlobId
)
--RETURN #XmlSchema.query('</xs:schema>')-- missing matching begin tag
--RETURN #XmlSchema.query('<xs:schema xmlns="" xmlns:xs="http://www.w3.org/2001/XMLSchema" xmlns:msdata="urn:schemas-microsoft-com:xml-msdata" id="NewDataSet">')-- Expected end tag 'xs:schema'
RETURN #XmlSchema.query('<xs:schema xmlns="" xmlns:xs="http://www.w3.org/2001/XMLSchema" xmlns:msdata="urn:schemas-microsoft-com:xml-msdata" id="NewDataSet"></xs:schema>')-- nothing in between was returned
END
GO
SELECT [etl].[ufn_GetXmlSchema]('A257667D-C3AA-471C-9F82-91FA35181833')
Any help is appreciated.

Answer 1

While waiting for a real scenario, here is a good jump start for you. As end result, it creates an XML Schema Collection named dbo.StateAndCities.
SQL
USE tempdb;
GO
-- DDL and sample data population, start
IF EXISTS (SELECT * FROM sys.xml_schema_collections
WHERE name = N'StateAndCities'
AND schema_id = SCHEMA_ID(N'dbo'))
DROP XML SCHEMA COLLECTION dbo.StateAndCities;
DECLARE #tbl TABLE (
ID INT IDENTITY PRIMARY KEY
, state CHAR(2)
, city VARCHAR(30)
);
INSERT INTO #tbl (state, city)
VALUES
('FL', 'Miami')
, ('CA', 'Los Angeles')
, ('TX', 'Austin');
-- DDL and sample data population, end
DECLARE #xml XML
, #XSD XML;
-- Generate XML plus embedded XSD schema
SET #xml = (SELECT NULL,
(
SELECT *
FROM #tbl AS [row]
FOR XML AUTO, ELEMENTS, TYPE, XMLSCHEMA('MyURI'))
FOR XML PATH(''), TYPE, ROOT('root')
);
-- just to see, XML plus embedded XSD schema
SELECT #xml;
-- retrive just XSD
;WITH xmlnamespaces ('http://www.w3.org/2001/XMLSchema' AS xsd)
SELECT #xsd = (SELECT #xml.query('/root/xsd:schema'));
-- just to see, XSD schema
SELECT #xsd AS xsd;
-- create schema collection
CREATE XML SCHEMA COLLECTION dbo.StateAndCities AS #xsd;