Parse field form xml clob - sql

Question

Ciao,
i've one problem with sql.
I've some table with datatype clob where is stored a clob.
In the same table if we have the xml format we use one function for take the xml_fied
CREATE OR REPLACE FUNCTION gettagvalue (
XMLBody IN CLOB, TagXml IN VARCHAR2) RETURN VARCHAR2 IS
BEGIN
return TO_CHAR (SUBSTR (XMLBody,
INSTR (XMLBody, '<'||TagXml||'>') + length(TagXml) + 2,
INSTR (XMLBody, '</'||TagXml||'>')
- INSTR (XMLBody, '<'||TagXml||'>')
- (length(TagXml) + 2)
)
);
END GetTagValue;
/
example :
Select errorhandler.GetTagValue(xml_content,'ORDERID')
from table_order
On the same table we have also some xml in json.
How i can create a copy of same function for take the field?
On xml is eay because we have the field with same name that start with and finish with but with json
I cannot understand how define the end of field

Answer 1

Do NOT try to parse XML or JSON as strings; use a proper XML or JSON parser.
If you have the table with the sample data:
CREATE TABLE table_name (
xml CLOB,
json CLOB CHECK ( json IS JSON )
);
INSERT INTO table_name ( xml, json ) VALUES (
'<a><b>BBB</b><c>CCC</c><d>DDD</d></a>',
'{"a":"aaa","b":"bbb","c":[1,2,3,4],"d":"ddd"}'
);
Then you can get the c values from both using the XMLQUERY or JSON_QUERY functions:
SELECT XMLQUERY(
'*/c/text()'
PASSING XMLTYPE(xml)
RETURNING CONTENT
) AS c_xml_value,
JSON_QUERY(
json,
'$.c'
RETURNING VARCHAR2(50)
) AS c_json_value
FROM table_name
Which outputs:
| C_XML_VALUE | C_JSON_VALUE |
| :---------- | :----------- |
| CCC | [1,2,3,4] |
If you have XML and JSON values in the same column then look at whether the first character is < or not and use the appropriate parsing function; do not try and create your own function to parse the values using substring matching.
For example:
CREATE TABLE table_name ( value CLOB );
INSERT INTO table_name ( value )
SELECT '<a><b>BBB</b><c>CCC</c><d>DDD</d></a>' FROM DUAL UNION ALL
SELECT '{"a":"aaa","b":"bbb","c":[1,2,3,4],"d":"ddd"}' FROM DUAL;
Then:
SELECT CASE
WHEN value LIKE '<%'
THEN CAST(
XMLQUERY( '*/c/text()' PASSING XMLTYPE(value) RETURNING CONTENT )
AS VARCHAR2(50)
)
ELSE JSON_QUERY( value, '$.c' RETURNING VARCHAR2(50) )
END AS c_value
FROM table_name
Outputs:
| C_VALUE |
| :-------- |
| CCC |
| [1,2,3,4] |
db<>fiddle here
Update
You can also use JSON_TABLE and XMLTABLE to get all the values out:
SELECT COALESCE( j.sourceChannel, x.sourceChannel ) AS sourceChannel,
COALESCE( j.transactionId, x.transactionId ) AS transactionId,
COALESCE( j.sessionId, x.sessionId ) AS transactionId,
COALESCE( j.status, x.status ) AS status,
COALESCE( j.errorcode, x.errorcode ) AS errorcode,
COALESCE( j.errordescription, x.errordescription ) AS errordescription
FROM table_name t
OUTER APPLY JSON_TABLE(
t.value,
'$.header'
COLUMNS (
sourceChannel VARCHAR2( 50) PATH '$.sourceChannel',
transactionId VARCHAR2( 50) PATH '$.transactionId',
sessionId VARCHAR2( 50) PATH '$.sessionId',
status VARCHAR2( 50) PATH '$.status',
errorcode VARCHAR2( 50) PATH '$.errorcode',
errordescription VARCHAR2(200) PATH '$.errordescription'
)
) j
LEFT OUTER JOIN LATERAL(
SELECT *
FROM XMLTABLE(
'/header'
PASSING XMLTYPE( value )
COLUMNS
sourceChannel VARCHAR2( 50) PATH 'sourceChannel',
transactionId VARCHAR2( 50) PATH 'transactionId',
sessionId VARCHAR2( 50) PATH 'sessionId',
status VARCHAR2( 50) PATH 'status',
errorcode VARCHAR2( 50) PATH 'errorcode',
errordescription VARCHAR2(200) PATH 'errordescription'
)
) x
ON ( t.value LIKE '<%' )
Which for the sample data:
CREATE TABLE table_name ( value CLOB );
INSERT INTO table_name ( value )
SELECT '<header>
<sourceChannel>xaaa</sourceChannel>
<transactionId>xbbb</transactionId>
<sessionId>xccc</sessionId>
<status>xddd</status>
<errorcode>xeee</errorcode>
<errordescription>xfff</errordescription>
</header>' FROM DUAL UNION ALL
SELECT '{"header":{"sourceChannel":"jaaa","transactionId":"jbbb","sessionId":"jccc","status":"jddd","errorcode":"jeee","errordescription":"jfff"}}' FROM DUAL;
Outputs:
SOURCECHANNEL
TRANSACTIONID
TRANSACTIONID
STATUS
ERRORCODE
ERRORDESCRIPTION
xaaa
xbbb
xccc
xddd
xeee
xfff
jaaa
jbbb
jccc
jddd
jeee
jfff