CLOB Vs XMLTYPE

Question

Hi Guys,
In one of my applications , From the front end we are getting XML data and storing the xml data in the col of table which is CLOB type .
Today one of the application developer told that directly we can store the xml data into the data base.Could any one tell me the difference in storing the data in the clob and xml
and also what is the advantages of using xml over clob data type.
Any suggestions will be highly appreciated.
Thanks,
Prafulla

Answer 1

Prafulla wrote:
Hi Guys,
In one of my applications , From the front end we are getting XML data and storing the xml data in the col of table which is CLOB type .
Today one of the application developer told that directly we can store the xml data into the data base.Could any one tell me the difference in storing the data in the clob and xml
and also what is the advantages of using xml over clob data type.
Any suggestions will be highly appreciated.
Thanks,
PrafullaXMLTYPE is based on the CLOB datatype under the hood. CLOB simply stores a whole stream of characters in one large chunk and you need to use the DBMS_LOB package to pull out any sort of structured information from that CLOB. XMLTYPE on the other hand understands that the content is XML and provides various methods for accessing the data as well as SQL being able to access the XML in a structured manner too.
For example, if you have some XML in an XMLTYPE, you can use the XMLTABLE keyword in SQL to extract the data from it e.g..
WITH t as (select XMLTYPE('
<RECSET>
  <REC>
    <COUNTRY>1</COUNTRY>
    <POINT>1800</POINT>
    <USER_INFO>
      <USER_ID>1</USER_ID>
      <TARGET>28</TARGET>
      <STATE>6</STATE>
      <TASK>12</TASK>
    </USER_INFO>
    <USER_INFO>
      <USER_ID>5</USER_ID>
      <TARGET>19</TARGET>
      <STATE>1</STATE>
      <TASK>90</TASK>
    </USER_INFO>
  </REC>
  <REC>
    <COUNTRY>2</COUNTRY>
    <POINT>2400</POINT>
    <USER_INFO>
      <USER_ID>3</USER_ID>
      <TARGET>14</TARGET>
      <STATE>7</STATE>
      <TASK>5</TASK>
    </USER_INFO>
  </REC>
</RECSET>') as xml from dual)
-- END OF TEST DATA
select x.country, x.point, y.user_id, y.target, y.state, y.task
from t
    ,XMLTABLE('/RECSET/REC'
              PASSING t.xml
              COLUMNS country NUMBER PATH '/REC/COUNTRY'
                     ,point   NUMBER PATH '/REC/POINT'
                     ,user_info XMLTYPE PATH '/REC/*'
             ) x
    ,XMLTABLE('/USER_INFO'
              PASSING x.user_info
              COLUMNS user_id NUMBER PATH '/USER_INFO/USER_ID'
                     ,target  NUMBER PATH '/USER_INFO/TARGET'
                     ,state   NUMBER PATH '/USER_INFO/STATE'
                     ,task    NUMBER PATH '/USER_INFO/TASK'
             ) y
   COUNTRY      POINT    USER_ID     TARGET      STATE       TASK
         1       1800          1         28          6         12
         1       1800          5         19          1         90
         2       2400          3         14          7          5It uses XQuery expressions to reference the data, so you can reference attributes of the XML elements as well as their values, and you can also use namespaces if those are needed. The above is just a simple example with some nested repeating groups.
If you tried to extract that data using a CLOB, you'd struggle to do that in SQL easily.