请问？如何将多个long raw型数值连接到一起

Question

CAST_TO_VARCHAR2 Function
This function converts a RAW represented using n data bytes into VARCHAR2 with n data bytes.
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Note: 
When casting to a VARCHAR2, the current Globalization Support character set is used for the characters within that VARCHAR2.--------------------------------------------------------------------------------
 Syntax
UTL_RAW.CAST_TO_VARCHAR2 (
   r IN RAW) 
  RETURN VARCHAR2;
select utl_raw.cast_to_varchar2(col) from tabname;