Benefits of quering XML nodes from XML columns

Since XML documents are already parsed at insert time, they are stored and ready to be queried in tree structure of nodes. This characteristic provides a much higher search and extraction performance.

Although there may be potential overhead of XML documents being parsed at insert time, it is often outweighed by the fact that XML columns are buffered in the buffer pools while large CLOB columns are not.

Drawbacks of quering XML nodes from CLOB columns

Without XML parsing, the structure of the XML documents is entirely ignored. This precludes the database from performing intelligent and efficient search and extract operations on the stored text objects. The only remedy is to invoke the XML parser at query execution time to "look into" the XML documents such that search conditions can be evaluated.

Query performance comparison

On the right pane, click the buttons in order to obtain an average query times for XML node data stored in XML columns and CLOB columns. You should see a better query performance with XML columns.