Query an xml (stored in varchar) in sql server - sql-server

Question

I have a database table which is structured as shown below :
TransactionId Product ErrorXML(stored as varchar)
The ErrorXML has the structure below :
<?xml version="1.0" encoding="utf-16"?>
<GetResponse
xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
xmlns:xsd="http://www.w3.org/2001/XMLSchema">
<Error>
<ErrorCode>1809</ErrorCode>
<Description>Could not generate transaction.</Description>
</Error>
<Success>false</Success>
<ContractNumber />
</GetResponse>
I would like to write a query to extract the ErrorCode element and ErrorDescription element for each of the Errorxml row .
Is there a way I can do it ?
I did some research and tried writing a query something like this and it wouldnt work , gives out a null:
select CONVERT(XML,CONVERT(NVARCHAR(max),ErrorXML)).value('(/GetResponse/Error/Description)[1]','nvarchar(100)') as ErrorDescription
from ErrorLog E

Answer 1

Here's a working SQL Fiddle
The Output
ErrorCode ErrorDescription
1809 Could not generate transaction.
2119 Credit Card Overlimit.Payment Failed.
The SQL
See the SQL fiddle for why we have to use a TABLE variable due to your data being in VARCHAR and not XML datatype.
--SELECT * FROM Transactions
DECLARE #ErrorDataTable TABLE
(
ErrorXml XML NOT NULL,
ErrorCode NVARCHAR(50) NULL,
ErrorDescription NVARCHAR(200) NULL
)
INSERT
INTO #ErrorDataTable(ErrorXml)
SELECT
CONVERT(XML,CONVERT(NVARCHAR(max),T.ErrorXML))
FROM Transactions T
-- SELECT * FROM #ErrorDataTable
SELECT
T.c.value('ErrorCode[1]', 'nvarchar(50)') as ErrorCode
, T.c.value('Description[1]', 'nvarchar(200)') as ErrorDescription
FROM #ErrorDataTable e
OUTER APPLY e.ErrorXml.nodes('/GetResponse/Error') T(c);
Previous Answer (deprecated)
Following Works. I'll try to put a SQLFiddle together.
DECLARE #ErrorXML as VARCHAR(MAX);
DECLARE #x as XML;
SET #ErrorXML ='<?xml version="1.0" encoding="utf-16"?>
<GetResponse
xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
xmlns:xsd="http://www.w3.org/2001/XMLSchema">
<Error>
<ErrorCode>1809</ErrorCode>
<Description>Could not generate transaction.</Description>
</Error>
<Success>false</Success>
<ContractNumber />
</GetResponse>';
SET #x = CONVERT(XML,CONVERT(NVARCHAR(max),#ErrorXML))
SELECT
T.c.value('ErrorCode[1]', 'nvarchar(50)') as ErrorCode
, T.c.value('Description[1]', 'nvarchar(200)') as ErrorDescription
FROM #x.nodes('/GetResponse/Error') T(c);
RESULTS:
ErrorCode ErrorDescription
1809 Could not generate transaction.