Oracle - BLOB and CLOB Comparison
You can store text data in BLOB columns, but Oracle does not allow you to compare data in BLOB and CLOB columns without casting. You can use the CAST_TO_VARCHAR2 function from the UTL_RAW package to perform the casting.
In the example below column_blob is BLOB, while column_clob is CLOB.
SELECT column_blob,column_clob FROM tables_lobs WHERE column_clob = utl_raw.cast_to_varchar2(dbms_lob.substr(column_blob))