
TO_CLOB converts NCLOB values in a LOB column or other character strings to CLOB values. char can be any of the data types CHAR, VARCHAR2, NCHAR, NVARCHAR2, CLOB, or NCLOB. Oracle Database executes this function by converting the underlying LOB data from the national character set to the database character set.
From within a PL/SQL package, you can use the TO_CLOB function to convert RAW, CHAR, VARCHAR, VARCHAR2, NCHAR, NVARCHAR2, CLOB, or NCLOB values to CLOB or NCLOB values.
The following statement converts NCLOB data from the sample pm.print_media table to CLOB and inserts it into a CLOB column, replacing existing data in that column.
UPDATE PRINT_MEDIA SET AD_FINALTEXT = TO_CLOB (AD_FLTEXTN);