Q. How to select named element values from XSD string field - sql

Question

Within SQL Server I'm trying to select values from what I think is a XSD string.
e.g. Given the following SQL Server table
CREATE TABLE dbo.TextXML (
ID INT PRIMARY KEY,
Data NVARCHAR(max))
INSERT INTO dbo.TextXML ( ID, Data )
SELECT 1,
('<element name="Rownum" value="Row23" />
<element name="CONNECTIONTYPESECTION" value="True" />
<element name="CustomFields" />
<element name="EchoData">
<element name="0000" value="8220000000000000" />
<element name="0001" value="0400000100000000" />
<element name="0007" value="0805193143" />
<element name="MessageType" value="1234" />
</element>
<element name="ENABLESSL" value="false" />' )
INSERT INTO dbo.TextXML ( ID, Data )
SELECT 2,
('<element name="Rownum" value="Row24" />
<element name="CONNECTIONTYPESECTION" value="True" />
<element name="CustomFields" />
<element name="EchoData">
<element name="0000" value="8220000000000000" />
<element name="0001" value="0400000100000000" />
<element name="0007" value="0805193143" />
<element name="MessageType" value="5678" />
</element>
<element name="ENABLESSL" value="true" />' );
I want to be able to select the values for given element names. Something like ...
SELECT ID, Data.CONNECTIONTYPESECTION, Data.EchoData.0007, Data.EchoData.MessageType, Data.ENABLESSL
FROM TextXML
WHERE Data.Rownum = "Row23" AND Data.EchoData.MessageType = "1234".
ID Data.CONNECTIONTYPESECTION Data.EchoData.0007 Data.EchoData.MessageType Data.ENABLESSL
1 True 0805193143 1234 true
I can use CHARINDEX and SUBSTRING but have to hardcode the length of the "name" value and this asumes the "value" is always the same length. I'm hoping there is a better and more efficient way do do this.
I have experimented with CROSS APPPLY and XML VALUE functions but this only returns the first element in the Data field. I also could not find out how to search for a particular element "name" to get its value

Answer 1

Please try the following T-SQL.
-- DDL and sample data population, start
DECLARE #tbl TABLE (ID INT IDENTITY PRIMARY KEY, Data NVARCHAR(max));
INSERT INTO #tbl (Data) VALUES
(N'<element name="Rownum" value="Row23"/>
<element name="CONNECTIONTYPESECTION" value="True"/>
<element name="CustomFields"/>
<element name="EchoData">
<element name="0000" value="8220000000000000"/>
<element name="0001" value="0400000100000000"/>
<element name="0007" value="0805193143"/>
<element name="MessageType" value="1234"/>
</element>
<element name="ENABLESSL" value="false"/>'),
(N'<element name="Rownum" value="Row24"/>
<element name="CONNECTIONTYPESECTION" value="True"/>
<element name="CustomFields"/>
<element name="EchoData">
<element name="0000" value="8220000000000000"/>
<element name="0001" value="0400000100000000"/>
<element name="0007" value="0805193143"/>
<element name="MessageType" value="5678"/>
</element>
<element name="ENABLESSL" value="true"/>');
-- DDL and sample data population, end
;WITH rs AS
(
SELECT *
, TRY_CAST(data AS XML) AS xmldata
FROM #tbl
)
SELECT rs.ID
, xmldata.value('(element[#name="CONNECTIONTYPESECTION"]/#value)[1]','VARCHAR(10)') AS CONNECTIONTYPESECTION
, xmldata.value('(element[#name="EchoData"]/element[#name="0007"]/#value)[1]','VARCHAR(10)') AS [EchoData.0007]
, xmldata.value('(element[#name="EchoData"]/element[#name="MessageType"]/#value)[1]','VARCHAR(10)') AS [EchoData.MessageType]
, xmldata.value('(element[#name="ENABLESSL"]/#value)[1]','VARCHAR(10)') AS [Data.ENABLESSL]
FROM rs
WHERE xmldata.value('(element[#name="Rownum"]/#value)[1]','VARCHAR(30)') = 'Row23'
AND xmldata.value('(element[#name="EchoData"]/element[#name="MessageType"]/#value)[1]','VARCHAR(10)') = '1234';
Output
+----+-----------------------+---------------+----------------------+----------------+
| ID | CONNECTIONTYPESECTION | EchoData.0007 | EchoData.MessageType | Data.ENABLESSL |
+----+-----------------------+---------------+----------------------+----------------+
| 1 | True | 0805193143 | 1234 | false |
+----+-----------------------+---------------+----------------------+----------------+