How to Parse XML Store in a CLOB in a SQL

Question

I'm rather new in using XML concepts in a SQL. Here is my dilemma:
I have a table with following definition:
CREATE TABLE extension
extension_id NUMBER(10) NOT NULL,
extension_content CLOB NOT NULL,
fk_transaction_id NUMBER(10),
fk_batch_id NUMBER(10)
Where XML format type data is stored and here is sample of data there:
INSERT INTO EXTENSION ( EXTENSION_ID, EXTENSION_CONTENT, FK_TRANSACTION_ID,
FK_BATCH_ID ) VALUES (
300, '<Extension>
<controlNumber>5070</controlNumber>
<depositDate1>031105</depositDate1>
<depositDate2>031105</depositDate2>
<recordType>7</recordType>
<sequenceNo>1</sequenceNo>
<statementNo>B5653047</statementNo>
</Extension>'
, 207, NULL);
INSERT INTO EXTENSION ( EXTENSION_ID, EXTENSION_CONTENT, FK_TRANSACTION_ID,
FK_BATCH_ID ) VALUES (
301, '<Extension>
<controlNumber>5070</controlNumber>
<depositDate1>031105</depositDate1>
<depositDate2>031105</depositDate2>
<recordType>7</recordType>
<sequenceNo>2</sequenceNo>
<statementNo>B5653047</statementNo>
</Extension>'
, 208, NULL);
INSERT INTO EXTENSION ( EXTENSION_ID, EXTENSION_CONTENT, FK_TRANSACTION_ID,
FK_BATCH_ID ) VALUES (
586, '<Extension>
<controlNumber>5157</controlNumber>
<headerId>ID UEA13700 CLASS C NAME</headerId>
<recordType>7</recordType>
</Extension>'
, NULL, 538);
INSERT INTO EXTENSION ( EXTENSION_ID, EXTENSION_CONTENT, FK_TRANSACTION_ID,
FK_BATCH_ID ) VALUES (
290, '<Extension>
<depositDate>40521</depositDate>
<destination exception="empty"></destination>
<x1Number>845734</x1Number>
<origin>21000021</origin>
<overflowCount>0</overflowCount>
</Extension>'
, NULL, 217);
Could you kindly help me to write a SQL which will retrieve the first rows where there are <controlNumber>, <depositDate1> and <depositDate2> in the column as?:
SELECT extension_id, ?extension_content? controlnumber, ??extension_content?? depositdate1, ???extension_content??? depositdate3 FROM Extension
WHERE...
The only way I could do was using several SUBSTR and INSTR on TO_CHAR(extension_content) which I don't think was a good way.
Thank you very much in advance for your help and your sample example.
Adam Tadj.

Answer 1

if you want to do it with SQL you should change the data type of the EXTENSION_CONTENT from CLOB to XMLTYPE so that you can treat the content in the column as XML and use functions (EXTRACT, EXTRACTVALUE etc...) available in the database to retrieve what you want.
but for this your database version should be atleast 9.2.0.4 and above.
here is the modified example.
CREATE TABLE extension
extension_id NUMBER(10) NOT NULL,
extension_content XMLTYPE NOT NULL,
fk_transaction_id NUMBER(10),
fk_batch_id NUMBER(10)
INSERT INTO EXTENSION ( EXTENSION_ID, EXTENSION_CONTENT, FK_TRANSACTION_ID,
FK_BATCH_ID ) VALUES (
300, xmltype('<Extension>
<controlNumber>5070</controlNumber>
<depositDate1>031105</depositDate1>
<depositDate2>031105</depositDate2>
<recordType>7</recordType>
<sequenceNo>1</sequenceNo>
<statementNo>B5653047</statementNo>
</Extension>')
, 207, NULL);
INSERT INTO EXTENSION ( EXTENSION_ID, EXTENSION_CONTENT, FK_TRANSACTION_ID,
FK_BATCH_ID ) VALUES (
301, xmltype('<Extension>
<controlNumber>5070</controlNumber>
<depositDate1>031105</depositDate1>
<depositDate2>031105</depositDate2>
<recordType>7</recordType>
<sequenceNo>2</sequenceNo>
<statementNo>B5653047</statementNo>
</Extension>')
, 208, NULL);
INSERT INTO EXTENSION ( EXTENSION_ID, EXTENSION_CONTENT, FK_TRANSACTION_ID,
FK_BATCH_ID ) VALUES (
586, xmltype('<Extension>
<controlNumber>5157</controlNumber>
<headerId>ID UEA13700 CLASS C NAME</headerId>
<recordType>7</recordType>
</Extension>')
, NULL, 538);
INSERT INTO EXTENSION ( EXTENSION_ID, EXTENSION_CONTENT, FK_TRANSACTION_ID,
FK_BATCH_ID ) VALUES (
290, xmltype('<Extension>
<depositDate>40521</depositDate>
<destination exception="empty"></destination>
<x1Number>845734</x1Number>
<origin>21000021</origin>
<overflowCount>0</overflowCount>
</Extension>')
, NULL, 217);
set linesize 1000
column extension_id format 999999
column controlnumber format 999999
select EXTENSION_ID
,extractvalue(EXTENSION_CONTENT, '/Extension/controlNumber') ControlNumber
,extractvalue(EXTENSION_CONTENT, '/Extension/depositDate') DepositDate
from extension
/