Similar to EMPTY_BLOB, the Oracle EMPTY_CLOB function is used for the initialization of CLOB columns in the table. As a reminder, note that empty CLOB does not mean a LOB of zero length.
During TABLE definitions, EMPTY_CLOB can be used to set default value of a column:
CREATE TABLE XML_TAB
XMLDOC CLOB DEFAULT EMPTY_CLOB);
The UPDATE statement below would set the XMLDOC column of the table XML_TAB to empty CLOB.
SET XMLDOC = EMPTY_CLOB();
1 row updated.