SQL & PL/SQL

I have a BLOB field in one of the table, where a big XML is stored.

I guess it is stored in BASE64 encoded.

I need to read the XML and get a value from one of the node and use it in a where clause.

All these I need to do using plain SQL, no PL/SQL.

I cannot touch or alter or do anything with the schema

Regards,

Anoop